Methods and compositions for concrete production

ABSTRACT

The invention provides compositions and methods directed to carbonation of a cement mix during mixing. The carbonation may be in a stationary mixer or a transportable mixer, such as a drum of a ready-mix truck.

CROSS-REFERENCE

This application is a continuation of U.S. patent application Ser. No.14/950,288, filed Nov. 24, 2015, which is a continuation-in-part of U.S.patent application Ser. No. 14/701,456, filed Apr. 30, 2015, which is acontinuation of PCT Application No. PCT/CA2014/050611 filed Jun. 25,2014, which claims the benefit of U.S. Provisional Patent ApplicationSer. No. 61/980,505, filed Apr. 16, 2014 and is a continuation-in-partof U.S. patent application Ser. No. 14/249,308, filed Apr. 9, 2014 (nowU.S. Pat. No. 9,108,883 issued Aug. 18, 2015), which claim the benefitof U.S. Provisional Patent Application Ser. No. 61/839,312, filed Jun.25, 2013, U.S. Provisional Patent Application Ser. No. 61/847,254, filedJul. 17, 2013, U.S. Provisional Patent Application Ser. No. 61/879,049,filed Sep. 17, 2013, U.S. Provisional Patent Application Ser. No.61/925,100, filed Jan. 8, 2014, U.S. Provisional Patent Application Ser.No. 61/938,063, filed Feb. 10, 2014. This application also claims thebenefit of U.S. Provisional Patent Application Ser. No. 62/083,784,filed Nov. 24, 2014, U.S. Provisional Patent Application Ser. No.62/096,018, filed Dec. 23, 2014, U.S. Provisional Patent ApplicationSer. No. 62/160,350, filed May 12, 2015, U.S. Provisional PatentApplication Ser. No. 62/165,670 filed May 22, 2015, U.S. ProvisionalPatent Application Ser. No. 62/240,843, filed Oct. 13, 2015, U.S.Provisional Patent Application Ser. No. 62/086,024, filed Dec. 1, 2014,and U.S. Provisional Patent Application Ser. No. 62/146,103, filed Apr.10, 2015, all of which are incorporated herein by reference in theirentireties.

BACKGROUND

Cement mixes, such as concrete mixes, are used in a multitude ofcompositions and procedures throughout the world. In addition,greenhouse gases such as carbon dioxide are a growing concern worldwide.There is a need for methods and compositions to contact cement mixeswith carbon dioxide and for cement mixes containing incorporated carbondioxide and carbonation products.

SUMMARY OF THE INVENTION

In one aspect, the invention provides methods.

In certain embodiments, the invention provides a method for carbonatinga concrete mix comprising a type of cement that includes delivering doseof CO2 to the concrete mix while it is mixing in a mixer, where thedelivery of the carbon dioxide commences within 3 minutes of the startof mixing of the concrete mix, and wherein the duration of the deliveryof the carbon dioxide is 10 seconds to 4 minutes. In certainembodiments, the dose of carbon dioxide is 0.01-1.0% by weight cement(bwc). In certain embodiments, the delivery of the carbon dioxidecommences within 1 minute of the start of mixing of the concrete mix.The mixer can be any suitable mixer, such as a stationary mixer or atransportable mixer; in certain embodiments, the mixer comprises atransportable mixer, e.g., a drum of a ready-mix truck. In certainembodiments, the dose of carbon dioxide is based on previous testing ofa plurality of doses of carbon dioxide on a plurality of test mixes,wherein the test mixes comprise the type of cement in the concrete mix,for example at least three test doses of carbon dioxide can be used inthe previous testing. In certain embodiments, the plurality of doses ofcarbon dioxide used in the previous testing are all 0.01-1.0% bwc, andthe dose of carbon dioxide delivered to the mixing concrete is 0.01-1.0%bwc. The carbon dioxide can be delivered via a conduit to the surface ofthe mixing concrete, for example, a conduit positioned to be 5-200 cmfrom the surface of the mixing concrete, on average. In certainembodiments, the carbon dioxide is delivered as a mixture of solid andgaseous carbon dioxide.

In certain embodiments, the invention provides a method for carbonatinga concrete mix in a drum of a ready-mix truck comprising (i) positioninga first conduit for delivery of components of the concrete mix to thedrum, wherein the first conduit contains a second conduit for deliveryof carbon dioxide to the concrete mix, and wherein the components of theconcrete mix comprise at least cement and water; (ii) delivering thecomponents of the concrete mix to the drum via the first conduit toprovide a concrete mix in the drum; (iii) mixing the concrete mix; and(iv) delivering a dose of carbon dioxide to the mixing concrete via anopening of the second conduit. In certain embodiments, the dose ofcarbon dioxide is 0.01-1.5% by weight cement. In certain embodiments,the carbon dioxide is a mixture of solid and gaseous carbon dioxide. Incertain embodiments, the dose of carbon dioxide is based on previoustesting of a plurality of doses of carbon dioxide on a plurality of testmixes, wherein the test mixes comprise the type of cement in theconcrete mix. In certain embodiments, at least three test doses ofcarbon dioxide are used in the previous testing. In certain embodiments,the plurality of doses of carbon dioxide used in the previous testingare all 0.01-1.0% bwc, and the dose of carbon dioxide delivered to themixing concrete is 0.01-1.0% bwc. In certain embodiments, the opening ofthe second conduit is positioned to be 5 cm to 200 cm, on average, froma surface of the mixing concrete.

In another aspect, the invention provides apparatus. In certainembodiments, the invention provides an apparatus for delivering carbondioxide to a drum of a ready-mix truck comprising (i) a first conduitconfigured for delivery of components of concrete to the drum of theready-mix truck; and (ii) a second conduit contained within or attachedto the first conduit configured for delivery of carbon dioxide to thedrum of the ready-mix truck. In certain embodiments the second conduitis made of material that is sufficiently flexible to move with the firstconduit. In certain embodiments, the second conduit contains a thirdconduit, wherein the third conduit is configured to be extended from thesecond conduit when the first conduit is positioned to deliver thecomponents of the concrete to the drum, and to be retracted when thefirst conduit is moved from the drum of the ready-mix truck

INCORPORATION BY REFERENCE

All publications, patents, and patent applications mentioned in thisspecification are herein incorporated by reference to the same extent asif each individual publication, patent, or patent application wasspecifically and individually indicated to be incorporated by reference.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features of the invention are set forth with particularity inthe appended claims. A better understanding of the features andadvantages of the present invention will be obtained by reference to thefollowing detailed description that sets forth illustrative embodiments,in which the principles of the invention are utilized, and theaccompanying drawings of which:

FIG. 1 provides a schematic view of a stationary mixer with apparatusfor providing carbon dioxide to a hydraulic cement mix during mixer.

FIG. 2 provides a schematic view of a mobile mixer (ready mix truck)provided with a detachable carbon dioxide delivery system to delivercarbon dioxide to the mixing concrete.

FIG. 3 provides a schematic view of a mobile mixer (ready mix truck)provided with an attached carbon dioxide delivery system to delivercarbon dioxide to the mixing concrete.

FIG. 4 shows 7-day compressive strengths of concrete prepared from wetmixes exposed to carbon dioxide at various doses.

FIG. 5 shows 7-day compressive strengths of concrete prepared from wetmixes exposed to carbon dioxide at various doses and with various watercontents.

FIG. 6 shows 7-day compressive strengths of concrete prepared from wetmixes exposed to carbon dioxide at various doses.

FIG. 7 shows 14-day compressive strengths of concrete prepared from wetmixes exposed to carbon dioxide at various doses.

FIG. 8 shows 28-day compressive strengths of concrete prepared from wetmixes exposed to carbon dioxide at various doses.

FIG. 9 shows 7-, 14-, and 28-day compressive strengths of concreteprepared from wet mixes exposed to carbon dioxide with two differentwater contents.

FIG. 10 shows 7- and 28-day compressive strengths of concrete preparedfrom wet mixes exposed to carbon dioxide at two different doses and twodifferent water contents.

FIG. 11 shows 7-day compressive strengths of concrete prepared from wetmixes exposed to carbon dioxide at two different doses and higher watercontent.

FIG. 12 shows 7-day compressive strengths of concrete prepared from wetmixes exposed to carbon dioxide at two different doses and higher watercontent.

FIG. 13 shows 7-day compressive strengths of concrete prepared from wetmixes exposed to carbon dioxide at two different doses and higher watercontent.

FIG. 14 shows slump of concrete wet mixes exposed to carbon dioxide attwo different doses and five different water contents.

FIG. 15 provides a graphic illustration of slump at various times aftertruck arrival for carbonated concrete batches prepared in a ready mixoperation.

FIG. 16 provides a graphic illustration of compressive strengthdevelopment in carbonated concrete prepared in a ready mix operation,compared to control, uncarbonated concrete, at 3, 7, 28, and 56 days.

FIG. 17A provides a graphic illustration of Rapid chloride penetrationtests

FIG. 17B provides a graphic illustration of Flexural strength tests oncarbonated concrete prepared in a ready mix operation compared tocontrol, uncarbonated concrete.

FIG. 18 provides a graphic illustration of compressive strengths at 1,7, 28, and 56 days for concretes prepared in a ready mix operation with0, 0.5, or 1.0% bwc carbon dioxide delivered to the concrete.

FIG. 19 provides a graphic illustration of compressive strengths at 1,7, 28, and 56 days for concretes prepared in a ready mix operation with0, 1.0, or 1.5% bwc carbon dioxide delivered to the concrete, and 0.05%sodium gluconate admixture added to the 1.5% batch.

FIG. 20 provides a graphic illustration of cylinder mass for constantvolume cylinders (density), a proxy for compressive strength, in drycast concrete prepared as uncarbonated or carbonated for 1 or 2 minutes,with addition of sodium gluconate admixture at various concentrations.

FIG. 21 provides a graphic illustration of cylinder mass for constantvolume cylinders (density), a proxy for compressive strength, in drycast concrete prepared as uncarbonated or carbonated for 90s at 50 LPMwith addition of sodium gluconate admixture at 0.24, 0.30, 0.36, or0.42% bwc.

FIG. 22 provides a graphic illustration of cylinder mass for constantvolume cylinders (density), a proxy for compressive strength, in drycast concrete prepared as uncarbonated or carbonated for 90s at 50 LPMwith addition of sodium gluconate admixture at 0.30 or 0.42% bwc.

FIG. 23 provides a graphic illustration of cylinder mass for constantvolume cylinders (density), a proxy for compressive strength, in drycast concrete prepared as uncarbonated or carbonated for 90s at 50 LPMwith addition of sodium gluconate admixture at 0.30 or 0.42% bwc. Allsamples included Rainbloc and Procast admixtures, with one 0.30% samplehaving Procast added after carbon dioxide delivery.

FIG. 24 provides a graphic illustration of slump, relative to untreatedcontrol, in carbonated mortar mixes treated with sodium glucoheptonate,fructose, or sodium gluconate at various concentrations.

FIG. 25 provides a graphic illustration of effects on slump of fructoseor sodium gluconate added to a mortar mix pre-, mid-, orpost-carbonation.

FIG. 26 provides a graphic illustration of effects on 24-hourcompressive strength, compared to uncarbonated control, of a carbonatedmortar preparation in which sodium gluconate was added either before orafter carbonation at doses of 0, 0.025, 0.05, and 0.75%.

FIG. 27 provides a graphic illustration of the effects of temperature ofmaterials on rate of carbon dioxide uptake in a mortar mix. Temperatureswere 7° C., 15° C. and 25° C.

FIG. 28 provides a graphic illustration of the effects of heated or coldgases, or dry ice, on carbon dioxide uptake in a cement paste system.

FIG. 29 provides a graphic illustration of the effects of plasticizersand calcium hydroxide on 24 hour compressive strength in carbonated anduncarbonated mortar mixes.

FIG. 30 provides a graphic illustration of the effects of CaO, NaOH,Ca(NO₂)₂, and CaCl₂ on 24 hour compressive strength in carbonated anduncarbonated mortar mix.

FIG. 31 provides a graphic illustration of the effect of carbon dioxideaddition before or after the addition of an air entrainer on mortardensity.

FIG. 32 provides a table showing the results of tests for carbon dioxideuptake, compressive strength, water absorption, and density for blocksproduced in a precast dry cast operation with carbonation at the mixer,feedbox, or both, in a standard block mix.

FIG. 33 is a graphic illustration of the effects of sodium gluconatedose on 7-, 28- and 56-day compressive strengths of carbonated blocksproduced in a dry cast operation, with various doses of sodiumgluconate, compared to uncarbonated control.

FIG. 34 provides a table showing the results of tests for carbon dioxideuptake, compressive strength, water absorption, and density for blocksproduced in a precast dry cast operation with carbonation at the mixerin a limestone block mix.

FIG. 35 provides a table showing the results of tests for carbon dioxideuptake, compressive strength, water absorption, and density for blocksproduced in a precast dry cast operation with carbonation at the mixerin a lightweight block mix.

FIG. 36 provides a graphic illustration of 7-, 28-, and 56-daycompressive strengths of lightweight blocks produced in a dry castoperation with carbonation and various doses of sodium gluconate.

FIG. 37 provides a table showing the results of tests for carbon dioxideuptake, compressive strength, water absorption, and density for blocksproduced in a precast dry cast operation with carbonation at the mixerin a sandstone block mix.

FIG. 38 provides a graphic illustration of 7-, 28-, and 56-daycompressive strengths of sandstone blocks produced in a dry castoperation with carbonation and various doses of sodium gluconate.

FIG. 39 provides a graphic illustration of the relationship betweenoptimum dose of sodium gluconate and cement content in carbonated drycast blocks.

FIG. 40 provides a graphic illustration of compressive strength anddensity of carbonated and uncarbonated precast medium weight blocks,with or without treatment with 0.25% sodium gluconate.

FIG. 41 provides a table of results of third party testing of mediumweight blocks produced in a precast operation as uncarbonated,carbonated, and carbonated+0.25% sodium gluconate, as strength,absorption, and shrinkage.

FIG. 42 provides a graphic illustration of the effect of cement type oncarbon dioxide uptake in a mortar mix.

FIG. 43 provides a graphic illustration of the effects of temperature ofmaterials on slump, relative to control, in carbonated mortar mixes.Temperatures were 7° C., 15° C. and 25° C.

FIG. 44 provides a graphic illustration of the effect of w/c ratio oncarbon dioxide uptake in a mortar mix.

FIG. 45 provides a graphic illustration of the effect of w/c ratio oncarbon dioxide uptake in a mortar mix.

FIG. 46 provides a graphic illustration of the effect of w/c ratio oncarbon dioxide uptake in a concrete mix.

FIG. 47 provides a graphic illustration of the relationship betweencarbon dioxide uptake and temperature rise in a mortar mix at variousw/c.

FIG. 48 provides a graphic illustration of the relationship betweencarbon dioxide uptake and temperature rise in mortar mixes prepared fromcements from Holcim GU, Lafarge Quebec, and Lehigh, at w/c of 0.5.

FIG. 49 provides a graphic illustration of the effects of sodiumgluconate at 0, 0.1%, or 0.2%, added after carbonation to a concrete mixon slump at 1, 10, and 20 minutes.

FIG. 50 provides a graphic illustration of the effects of fructose oninitial slump of carbonated concrete mix.

FIG. 51 provides a graphic illustration of the effects of fructose on24-hour and 7-day compressive strength in a carbonated concrete mix.

FIG. 52 provides a graphic illustration of the relationship betweensurface area compressive strength at 24 hours of carbonated mortarsproduced with different cements.

FIG. 53 provides a graphic illustration of carbon dioxide dosing (topline), carbon dioxide uptake (second line from top), and carbon dioxidedetected at two sensors (bottom two lines) in a precast mixing operationwhere carbon dioxide flow was adjusted according to the carbon dioxidedetected by the sensors.

FIG. 54 shows isothermal calorimetry curves in mortar prepared withHolcim GU cement carbonated at low levels of carbonation.

FIG. 55 shows total heat evolution at various time points in mortarprepared with Holcim GU cement carbonated at low levels of carbonation.

FIG. 56 shows set, as represented by penetrometer readings, in mortarprepared with Holcim GU cement carbonated at a low level of carbonation.

FIG. 57 shows isothermal calorimetry curves in mortar prepared withLafarge Brookfield GU cement carbonated at low levels of carbonation.

FIG. 58 shows 8 hour and 24 hour compressive strengths in mortarprepared with Lafarge Brookfield GU cement carbonated at low levels ofcarbonation.

FIG. 59 shows isothermal calorimetry curves in concrete prepared withLafarge Brookfield GU cement carbonated at low levels of carbonation.

FIG. 60 shows calorimetry energy curves in concrete prepared withLafarge Brookfield GU cement carbonated at low levels of carbonation.

FIG. 61 shows 8 hour and 12 hour compressive strengths in concreteprepared with Lafarge Brookfield GU cement carbonated at low levels ofcarbonation.

FIG. 62 shows set, as represented by penetrometer readings, in mortarprepared with Lafarge Brookfield GU cement carbonated at a low level ofcarbonation.

FIG. 63 shows 8 hour and 12 hour compressive strengths in concreteprepared with St. Mary's Bowmanville GU cement carbonated at low levelsof carbonation.

FIG. 64 shows 12-hour compressive strengths of concrete carbonated atvarious low doses of carbonation.

FIG. 65 shows 16-hour compressive strengths of concrete carbonated atvarious low doses of carbonation

FIG. 66 shows 24-hour compressive strengths of concrete carbonated atvarious low doses of carbonation.

FIG. 67 shows 7-day compressive strengths of concrete carbonated atvarious low doses of carbonation.

FIG. 68 shows carbon dioxide uptake of dry mix concrete at various dosesof sodium gluconate.

FIG. 69 shows compacted cylinder mass (a proxy for density) related tosodium gluconate dose in carbonated and uncarbonated dry mix concrete.

FIG. 70 shows the data of FIG. 69 normalized to control.

FIG. 71 shows 6 hour energy released related to sodium gluconate dose incarbonated and uncarbonated dry mix concrete.

FIG. 72 shows the data of FIG. 71 normalized to control.

FIG. 73 shows rates of CO₂ uptake in mortars prepared with added CaO,NaOH, or CaCl2, or no additive.

FIG. 74 shows a summary of calorimetry data for mortars prepared withand without added CaO and exposed to carbon dioxide for various lengthsof time while mixing, as well as carbon dioxide uptake.

FIG. 75 shows relative comparison of energy released by mortar mixeswith no added CaO subjected to carbonation, compared to uncarbonatedcontrol.

FIG. 76 shows a relative comparison of energy released by CaO-dopedmortar mixes exposed to carbon dioxide for various times, compared tomortar mixes with no added CaO exposed to carbon dioxide for the sametime periods.

FIG. 77A shows calorimetry data for the CO2-1, -2, and -3 mixes ofExample 28, and uncarbonated control, power vs. time.

FIG. 77B shows calorimetry data for the CO2-1, -2, and -3 mixes ofExample 28, and uncarbonated control, energy vs. time.

FIG. 78A shows calorimetry data for the CO2-4, -5, and -6 mixes ofExample 28, and uncarbonated control, power vs. time.

FIG. 78B shows calorimetry data for the CO2-4, -5, and -6 mixes ofExample 28, and uncarbonated control.

FIG. 79A shows calorimetry data for the CO2-1, -2, and -3 mixes ofExample 29, and uncarbonated control, power vs. time.

FIG. 79B shows calorimetry data for the CO2-1, -2, and -3 mixes ofExample 29, and uncarbonated control.

FIG. 80A shows calorimetry data for the CO2-5, and -6 mixes of Example29, and uncarbonated control, power vs. time.

FIG. 80B shows calorimetry data for the CO2-5, and -6 mixes of Example29, and uncarbonated control.

FIG. 81 shows compressive strengths at 24 hours for control and threedifferent doses of carbon dioxide of the first day of the trial ofExample 30.

FIG. 82 shows compressive strengths at 3 days for control and threedifferent doses of carbon dioxide of the first day of the trial ofExample 30.

FIG. 83 shows compressive strengths at 7 days for control and threedifferent doses of carbon dioxide of the first day of the trial ofExample 30.

FIG. 84 shows compressive strengths at 28 days for control and threedifferent doses of carbon dioxide of the first day of the trial ofExample 30.

FIG. 85 shows compressive strengths at 56 days for control and threedifferent doses of carbon dioxide of the first day of the trial ofExample 30.

FIG. 86A shows calorimetry data for the CO2-1 (1402), -2 (1403), and -3(1404) mixes of the first day of the trial of Example 30, anduncarbonated control (1401), power vs. time.

FIG. 86B shows calorimetry data for the CO2-1 (1402), -2 (1403), and -3(1404) mixes of the first day of the trial of Example 30, anduncarbonated control (1401), energy vs. time.

FIG. 87 shows compressive strengths at 24 hours for control and one doseof carbon dioxide of the second day of the trial of Example 30.

FIG. 88 shows compressive strengths at 3 days for control and one doseof carbon dioxide of the second day of the trial of Example 30.

FIG. 89 shows compressive strengths at 7 days for control and one doseof carbon dioxide of the second day of the trial of Example 30.

FIG. 90 shows compressive strengths at 28 days for control and one doseof carbon dioxide of the second day of the trial of Example 30.

FIG. 91 shows compressive strengths at 56 days for control and one doseof carbon dioxide of the second day of the trial of Example 30.

FIG. 92A shows calorimetry data for the CO2-1 and -2 mixes of the secondday of the trial of Example 30, and uncarbonated controls 1 and 2, powervs. time.

FIG. 92B shows calorimetry data for the CO2-1 and -2 mixes of the secondday of the trial of Example 30, and uncarbonated controls 1 and 2,energy vs. time.

FIG. 93A shows calorimetry data for the three doses of carbon dioxide ofExample 31, and uncarbonated control, power vs. time.

FIG. 93B shows calorimetry data for the three doses of carbon dioxide ofExample 31, and uncarbonated control, energy vs. time.

FIG. 94A shows calorimetry data for the two doses of carbon dioxide ofExample 32, and uncarbonated control, power vs. time.

FIG. 94B shows calorimetry data for the two doses of carbon dioxide ofExample 32, and uncarbonated control, energy vs. time.

FIG. 95 shows calorimetry curves for 5 mortars with varying levels ofCO₂ uptake (1 sample before carbonation followed by 5 rounds ofcarbonation, each for 2 min at 0.15 LPM) of Example 33.

FIG. 96 shows total energy released at 4 hours after mixing for the 4different levels of carbonation of Example 33, compared to uncarbonatedcontrol.

FIG. 97 shows total energy released at 8 hours after mixing for the 4different levels of carbonation of Example 33, compared to uncarbonatedcontrol.

FIG. 98 shows total energy released at 12 hours after mixing for the 4different levels of carbonation of Example 33, compared to uncarbonatedcontrol.

FIG. 99 shows total energy released at 16 hours after mixing for the 4different levels of carbonation of Example 33, compared to uncarbonatedcontrol.

FIG. 100 shows calorimetry as power vs. time for a mortar mix made withcarbonated mix water vs. uncarbonated mix water, as described in Example34.

FIG. 101 shows calorimetry as energy released vs. time for a mortar mixmade with carbonated mix water vs. uncarbonated mix water, as describedin Example 34.

FIG. 102 shows results for an Argos cement+Venture FA mix under threedifferent carbonation conditions, at three different times, as totalheat released relative to a control, uncarbonated mix, as described inExample 35.

FIG. 103 results for a Cemex cement+Venture FA mix under three differentcarbonation conditions, at three different times, as total heat releasedrelative to a control, uncarbonated mix, as described in Example 35.

FIG. 104 shows results for a Holcim cement+Venture FA mix under threedifferent carbonation conditions, at three different times, as totalheat released relative to a control, uncarbonated mix, as described inExample 35.

FIG. 105 shows results for a Titan Roanoake cement+Venture FA mix underthree different carbonation conditions, at three different times, astotal heat released relative to a control, uncarbonated mix, asdescribed in Example 35.

FIG. 106 shows results for an Argos cement+SEFA FA mix under threedifferent carbonation conditions, at three different times, as totalheat released relative to a control, uncarbonated mix, as described inExample 35.

FIG. 107 shows results for a Cemex cement+SEFA FA mix under threedifferent carbonation conditions, at three different times, as totalheat released relative to a control, uncarbonated mix, as described inExample 35.

FIG. 108 shows results for a Holcim cement+SEFA FA mix under threedifferent carbonation conditions, at three different times, as totalheat released relative to a control, uncarbonated mix, as described inExample 35.

FIG. 109 shows results for a Titan Roanoake cement+SEFA FA mix underthree different carbonation conditions, at three different times, astotal heat released relative to a control, uncarbonated mix, asdescribed in Example 35.

FIG. 110 shows calorimetry as power vs. time for a mortar mix made witha Roanoake cement-Trenton Class F fly ash 80/20 blend, carbonated for 2,4, or 6 min, as described in Example 36.

FIG. 111 shows calorimetry as energy released vs. time for a mortar mixmade with a Roanoake cement-Trenton Class F fly ash 80/20 blend,carbonated for 2, 4, or 6 min, as described in Example 36.

FIG. 112 shows calorimetry as power vs. time for a mortar mix made witha STMB cement-Trenton Class F fly ash 80/20 blend, carbonated for 2, 4,or 6 min, as described in Example 36.

FIG. 113 shows calorimetry as energy released vs. time for a mortar mixmade with a STMB cement-Trenton Class F fly ash 80/20 blend, carbonatedfor 2, 4, or 6 min, as described in Example 36.

FIG. 114 shows calorimetry as power vs. time for a mortar mix made witha STMB cement and three different doses of sodium bicarbonate, asdescribed in Example 37.

FIG. 115 shows calorimetry as energy released vs. time for a mortar mixmade with a STMB cement and three different doses of sodium bicarbonate,as described in Example 37.

FIG. 116 shows calorimetry as power vs. time for a mortar mix made witha LAFB cement and three different doses of sodium bicarbonate, asdescribed in Example 37.

FIG. 117 shows calorimetry as energy released vs. time for a mortar mixmade with a LAFB cement and three different doses of sodium bicarbonate,as described in Example 37.

FIG. 118 shows calorimetry as power vs. time for a mortar mix made witha STMB cement and two different times for addition of carbonated mixwater, as described in Example 38.

FIG. 119 shows calorimetry as energy released vs. time for a mortar mixmade with a STMB cement and two different times for addition ofcarbonated mix water, as described in Example 38.

FIG. 120 shows calorimetry as power vs. time for a mortar mix made witha LAFB cement and two different times for addition of carbonated mixwater, as described in Example 38.

FIG. 121 shows calorimetry as energy released vs. time for a mortar mixmade with a LAFB cement and two different times for addition ofcarbonated mix water, as described in Example 38.

FIG. 122 shows calorimetry as power vs. time for a mortar mix made witha LAFB cement and 5 different durations for addition of carbonated mixwater, as described in Example 38.

FIG. 123 shows calorimetry as energy released vs. time for a mortar mixmade with a LAFB cement and 5 different durations for addition ofcarbonated mix water, as described in Example 38.

FIG. 124 shows calorimetry as power vs. time for a mortar mix made witha STMB cement and a carbonated synthetic wash water, filtered orunfiltered, as described in Example 39.

FIG. 125 shows calorimetry as energy released vs. time for a mortar mixmade with a STMB cement and a carbonated synthetic wash water, filteredor unfiltered, as described in Example 39.

FIG. 126 shows calorimetry as power vs. time for a mortar mix made witha LAFB cement and carbonated for 2, 4, or 6 minutes, at 5 to 10° C., asdescribed in Example 40.

FIG. 127 shows calorimetry as energy released vs. time for a mortar mixmade with a LAFB cement and carbonated for 2, 4, or 6 minutes, at 5 to10° C., as described in Example 40.

FIG. 128 shows calorimetry as power vs. time for a mortar mix made witha LAFB cement and carbonated for 2, 4, or 6 minutes, at 10 to 15° C., asdescribed in Example 40.

FIG. 129 shows calorimetry as energy released vs. time for a mortar mixmade with a LAFB cement and carbonated for 2, 4, or 6 minutes, at 10 to15° C., as described in Example 40.

FIG. 130 shows calorimetry as power vs. time for a mortar mix made witha STMB cement and carbonated for 2, 4, or 6 minutes, at 5 to 10° C., asdescribed in Example 40.

FIG. 131 shows calorimetry as energy released vs. time for a mortar mixmade with a STMB cement and carbonated for 2, 4, or 6 minutes, at 5 to10° C., as described in Example 40.

FIG. 132 shows calorimetry as power vs. time for a mortar mix made witha STMB cement and carbonated for 2, 4, or 6 minutes, at 10 to 15° C., asdescribed in Example 40.

FIG. 133 shows calorimetry as energy released vs. time for a mortar mixmade with a STMB cement and carbonated for 2, 4, or 6 minutes, at 10 to15° C., as described in Example 40.

FIG. 134 shows the position at which the wand for carbon dioxidedelivery is aimed in the drum of a ready mix truck, at the second fin inthe truck on the bottom side of the drum.

FIG. 135 shows an extendable system for supplying carbon dioxide, suchas gaseous and solid carbon dioxide derived from liquid carbon dioxide,to the drum of a ready mix truck, where the system is attached to aflexible boot that delivers materials to the drum of the truck.

FIG. 136 shows the system of FIG. 135 in retracted and extendedpositions.

FIG. 137 shows an electron micrograph as described in Example 41.

FIG. 138 shows pore silicon concentration in cement mixes carbonated atdifferent levels of carbonation at 8 minutes and 30 minutes aftercarbonation.

FIG. 139 shows power curves for the carbonated mixes of FIG. 138.

FIG. 140 shows the effect of carbonation on initial set in cement mixesprepared with two different types of cement.

FIG. 141 shows the effect of carbonation on final set in cement mixesprepared with two different types of cement.

FIG. 142 shows 24-hour compressive strength in carbonated mortar mixescompared to control (uncarbonated) mortar mixes, where the only binderwas cement.

FIG. 143 shows 24-hour compressive strength in carbonated mortar mixescompared to control (uncarbonated) mortar mixes, where the binder wascement and class C fly ash.

FIG. 144 shows compressive strength results for 1, 3, 7, and 28 days forsamples in 12 different industrial trials of carbonation of concretemixes.

FIG. 145 shows slump results for samples in 12 different industrialtrials of carbonation of concrete mixes.

FIG. 146 shows air results for samples in 12 different industrial trialsof carbonation of concrete mixes.

FIG. 147 provides a schematic illustration of a typical volumetricconcrete truck

DETAILED DESCRIPTION I. Introduction

Carbon dioxide emissions are recognized as a significant issue relatingto cement production and the use of concrete as a building material. Itis estimated that 5% of the world's annual CO₂ emissions areattributable to cement production. The industry has previouslyrecognized a number of approaches to reduce the emissions intensity ofthe cement produced and used. The most significant improvements inefficiency and cement substitution are likely to be already known andavailable. Future emissions improvements will likely be incremental.Innovative approaches are sought that can be a part of a portfoliostrategy. Thus, a range of further approaches will also have to bepursued.

One potential method is to up cycle captured carbon dioxide intoconcrete products. The mechanism of the carbonation of freshly hydratingcement was systematically studied in the 1970s at the University ofIllinois. The main cement phases, tricalcium silicate and dicalciumsilicate, were shown to react with carbon dioxide in the presence ofwater to form calcium carbonate and calcium silicate hydrate gel asshown in equations 1 and 2:

3CaO.SiO₂+(3-x)CO₂ +yH₂O→xCaO.SiO₃ .yH₂O+(3-x)CaCO₃  (1)

2CaO.SiO₂+(2-x)CO₂ +yH₂O→xCaO.SiO₃ .yH2O+(2-x)CaCO₃  (2)

Further any free calcium hydroxide present in the cement paste willrapidly hydrate and react with carbon dioxide, as show in equation 3:

Ca(OH)₂+CO₂+H₂O→CaCO₃+2H₂O  (3)

The carbonation reactions are exothermic. The reaction proceeds in theaqueous state when Ca²⁺ ions from the cementitious phases meet CO₃ ²⁻ions from the applied gas. The carbonation heats of reaction for themain calcium silicate phases are 347 kJ/mol for C3S and 184 kJ/mol forβ-C2S and 74 kJ/mol for Ca(OH)₂.

When the calcium silicates carbonate, the calcium silicate hydrate(C—S—H) gel that forms is understood to be intermixed with CaCO₃. C—S—Hgel formation occurs even in an ideal case of β-C2S and C3S exposed to a100% CO₂ at 1 atm given the observation that the amount of carbonatethat forms does not exactly correspond to the amount of calcium silicateinvolved in the reaction.

The reaction of carbon dioxide with a mature concrete microstructure isconventionally acknowledged to be a durability issue due to such effectsas shrinkage, reduced pore solution pH, and carbonation inducedcorrosion. In contrast, a carbonation reaction integrated into concreteproduction reacts CO₂ with freshly hydrating cement, rather than thehydration phases present in mature concrete, and does not have the sameeffects. Rather, by virtue of adding gaseous CO₂ to freshly mixingconcrete the carbonate reaction products are anticipated to form insitu, be of nano-scale and be homogenously distributed.

The invention provides methods, apparatus, and compositions forproduction of materials comprising a cement binder, e.g., a hydrauliccement or non-hydraulic cement. “Cement mix,” as that term is usedherein, includes a mix of a cement binder, e.g., a hydraulic cement,such as a Portland cement, and water; in some cases, “cement mix”includes a cement binder mixed with aggregate, such as a mortar (alsotermed a grout, depending on consistency), in which the aggregate isfine aggregate; or “concrete,” which includes a coarse aggregate. Thecement binder may be a hydraulic or non-hydraulic cement, so long as itprovides minerals, e.g. calcium, magnesium, sodium, and/or potassiumcompounds such as CaO, MgO, Na₂O, and/or K₂O that react with carbondioxide to produce stable or metastable products containing the carbondioxide, e.g., calcium carbonate. An exemplary hydraulic cement isPortland cement. In general herein the invention includes descriptionsof hydraulic cement binder and hydraulic cement mixes, but it will beappreciated that any cement mix is envisioned, whether containing ahydraulic or non-hydraulic cement binder, so long as the cement binderis capable of forming stable or metastable products when exposed tocarbon dioxide, e.g., contains calcium, magnesium, sodium, and/orpotassium compounds such as CaO, MgO, Na₂O, and/or K₂O. In certainembodiments, the invention provides methods, apparatus, and compositionsfor production of a cement mix (concrete) containing cement, such asPortland cement, treated with carbon dioxide. As used herein, the term“carbon dioxide” refers to carbon dioxide in a gas, solid, liquid, orsupercritical state where the carbon dioxide is at a concentrationgreater than its concentration in the atmosphere; it will be appreciatedthat under ordinary conditions in the production of cement mixes(concrete mixes) the mix is exposed to atmospheric air, which containsminor amounts of carbon dioxide. The present invention is directed toproduction of cement mixes that are exposed to carbon dioxide at aconcentration above atmospheric concentrations.

Cement mix operations are commonly performed to provide cement mixes(concrete) for use in a variety of applications, the most common ofwhich is as a building material. Such operations include precastoperations, in which a concrete structure is formed in a mold from thecement mix and undergoes some degree of hardening before transport anduse at a location separate from the mix location, and ready mixoperations, in which the concrete ingredients are supplied at onelocation and generally mixed in a transportable mixer, such as the drumof a ready mix truck, and transported to a second location, where thewet mix is used, typically by being poured or pumped into a temporarymold. Precast operations can be either a dry cast operation or a wetcast operation, whereas ready mix operations are wet cast. Any otheroperation in which a concrete mix is produced in a mixer and exposed tocarbon dioxide during mixing is also subject to the methods andcompositions of the invention.

Without being bound by theory, when the cement mix (concrete) is exposedto carbon dioxide, the carbon dioxide first dissolves in mix water andthen forms intermediate species, before precipitating as a stable ormetastable species, e.g., calcium carbonate. As the carbonate speciesare removed from solution, further carbon dioxide may dissolve in thewater. In certain embodiments, the mix water contains carbon dioxidebefore exposure to the cement binder. All of these processes areencompassed by the term “carbonation” of the cement mix, as that term isused herein.

II. Components

In certain embodiments the invention provides methods for preparing amix containing cement, by contacting a mixture of a cement binder, e.g.,hydraulic cement and water, and, optionally, other components such asaggregate (a “cement mix”, or “concrete,” e.g., a “hydraulic cementmix”) with carbon dioxide during some part of the mixing of the cementmix, e.g., hydraulic cement mix.

In certain embodiments, a hydraulic cement is used. The term “hydrauliccement,” as used herein, includes a composition which sets and hardensafter combining with water or a solution where the solvent is water,e.g., an admixture solution. After hardening, the compositions retainstrength and stability even under water. An important characteristic isthat the hydrates formed from the cement constituents upon reaction withwater are essentially insoluble in water. A hydraulic cement used may beany hydraulic cement capable of forming reaction products with carbondioxide. The hydraulic cement most commonly used is based upon Portlandcement. Portland cement is made primarily from limestone, certain clayminerals, and gypsum, in a high temperature process that drives offcarbon dioxide and chemically combines the primary ingredients into newcompounds. In certain embodiments, the hydraulic cement in the hydrauliccement mix is partially or completely composed of Portland cement.

A “hydraulic cement mix,” as that term is used herein, includes a mixthat contains at least a hydraulic cement and water. Additionalcomponents may be present, such as aggregates, admixtures, and the like.In certain embodiments the hydraulic cement mix is a concrete mix, i.e.,a mixture of hydraulic cement, such as Portland cement, water, andaggregate, optionally also including an admixture.

The methods in certain embodiments are characterized by contactingcarbon dioxide with wet cement binder, e.g., hydraulic cement, in amixer at any stage of the mixing, such as during mixing of the cementwith water, or during the mixing of wetted cement with other materials,or both. The cement may be any cement, e.g., hydraulic cement capable ofproducing reaction products with carbon dioxide. For example, in certainembodiments the cement includes or is substantially all Portland cement,as that term is understood in the art. The cement may be combined in themixer with other materials, such as aggregates, to form acement-aggregate mixture, such as mortar or concrete. The carbon dioxidemay be added before, during, or after the addition of the othermaterials besides the cement and the water. In addition oralternatively, in certain embodiments the water itself may becarbonated, i.e., contain dissolved carbon dioxide.

In certain embodiments, the contacting of the carbon dioxide with thecement mix, e.g., hydraulic cement mix, may occur when part but not allof the water has been added, or when part but not all of the cement hasbeen added, or both. For example, in one embodiment, a first aliquot ofwater is added to the cement or cement aggregate mixture, to produce acement or cement-aggregate mixture that contains water in a certainwater/cement (w/c) ratio or range of w/c ratios. In some cases one ormore components of the cement mix, e.g., hydraulic cement mix, such asaggregate, may be wet enough that is supplies sufficient water so thatthe mix may be contacted with carbon dioxide. Concurrent with, or after,the addition of the water, carbon dioxide is introduced to the mixture,while the mixture is mixing in a mixer.

The carbon dioxide may be of any purity and/or form suitable for contactwith cement, e.g., hydraulic cement during mixing to form reactionproducts. As described, the carbon dioxide is at least above theconcentration of atmospheric carbon dioxide. For example, the carbondioxide may be liquid, gaseous, solid, or supercritical, or anycombination thereof. In certain embodiments, the carbon dioxide isgaseous when contacted with the cement, e.g., hydraulic cement, thoughit may be stored prior to contact in any convenient form, e.g., inliquid form. In alternative embodiments, some or all of the carbondioxide may be in liquid form and delivered to the cement or cement mix(concrete), e.g., in such a manner as to form a mixture of gaseous andsolid carbon dioxide; the stream of liquid carbon dioxide can beadjusted by, e.g., flow rate and/or orifice selection so as to achieve adesired ratio of gaseous to solid carbon dioxide, such as ratio ofapproximately 1:1, or within a range of ratios. The carbon dioxide mayalso be solid when delivered to the concrete, i.e., as dry ice; this isuseful when a controlled or sustained release of carbon dioxide isdesired, for example, in a ready mix truck in transit to a mix site, orother wet mix operations, as the dry ice sublimates over time to delivergaseous carbon dioxide to the mix; the size and shape of the dry iceadded to the mix may be manipulated to ensure proper dose and time ofdelivery. In certain embodiments the carbon dioxide is dissolved inwater and delivered to the cement or cement mix (concrete). The carbondioxide may also be of any suitable purity for contact with the cementor cement mix (concrete), e.g., hydraulic cement during mixing under thespecified contact conditions to form reaction products. In certainembodiments the carbon dioxide is more than 5, 10, 20, 30, 40, 50, 60,70, 80, 90, 95, or 99% pure. In certain embodiments, the carbon dioxideis more than 95% pure. In certain embodiments, the carbon dioxide ismore than 99% pure. In certain embodiments, the carbon dioxide is20-100% pure, or 30-100% pure, or 40-100% pure, or 50-100% pure, or60-100% pure, or 70-100% pure, or 80-100% pure, or 90-100% pure, or95-100% pure, or 98-100% pure, or 99-100% pure. In certain embodiments,the carbon dioxide is 70-100% pure. In certain embodiment, the carbondioxide is 90-100% pure. In certain embodiment, the carbon dioxide is95-100% pure. The impurities in the carbon dioxide may be any impuritiesthat do not substantially interfere with the reaction of the carbondioxide with the wet cement mix, e.g., hydraulic cement mix. Commercialsources of carbon dioxide of suitable purity are well-known.

The carbon dioxide, e.g., carbon dioxide gas, liquid, or solid, may becommercially supplied high purity carbon dioxide. In this case, thecommercial carbon dioxide, e.g., gas, liquid, or solid, may be sourcedfrom a supplier that processes spent flue gasses or other waste carbondioxide so that sequestering the carbon dioxide in the cement mix, e.g.,hydraulic cement mix sequesters carbon dioxide that would otherwise be agreenhouse gas emission.

In addition, because carbonation of a cement mix, e.g., a concrete mix,often produces an improvement in strength compared to uncarbonated mix,less cement can be used in the production of a concrete that is equal instrength. In some cases, the amount of carbon dioxide absorbed is modestbut if a consistent strength benefit can be realized then there ismotivation to optimize the process and reduce the cement content. Forexample, masonry producers generally do not have any internal orexternal motivation to produce product that has a strength 119% of theconventional product. Instead, an economic gain can be realized by usinga mix design that contains less cement and achieves, through help of thecarbonation process, 100% of the uncarbonated product strength. Areduced cement mix design would additionally have clear environmentalbenefits given that Portland cement clinker typically has embodied CO₂on the order of 866 kg CO_(2e)/tonne of clinker. If 5% of the cement wasremoved from the block mix design (about 333 kg/m³) then the emissionssavings would be around 14 kg/m³ concrete before including any netoffset related to the CO₂ absorption. Thus, in certain embodiments, theinvention provides a carbonated concrete composition comprising anamount of cement that is less than the amount of cement needed in anuncarbonated concrete composition of the same or substantially the samemix design, e.g., at least 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 15, 17,20, 25, 30, 40, or 50% less cement, but with a strength, e.g.,compressive strength, that is within 20, 15, 10, 5, 3, 2, or 1% of thecompressive strength of the uncarbonated concrete mix at a given time ortimes after mixing, such as 24 hours, 2 days, 7 days, 14 days, 21 days,56 days, or 91 days, or a combination thereof. These times are merelyexemplary and any time or combination of times that gives meaningfulinformation about the strength of the mix as related to its intended usemay be used. Such compositions realize a net savings in CO₂ emissionsthat includes the amount of carbon dioxide taken up by the composition,and the amount of carbon dioxide emission avoided because less cement isneeded in the production of the composition. For example, the netemission savings may be at least 1, 2, 3, 4, 5, 7, 10, 12, 15, 17, 20,25, 30, 35, 40, 45, 50, 60, 70, 80, 90, 100, 125, or 150 kg CO₂/m³ ofconcrete for the carbonated compared to the uncarbonated concrete. Theconcrete may be in the form of a precast object, such as a block, pipe,brick, paver, or the like; the concrete may be in the form of aready-mix concrete that is poured into molds at a job site. Thecarbonation of the concrete may produce nanocrystals of calciumcarbonate as described elsewhere herein. Substantial cost savings canalso be realized by decreasing the amount of cement for a given concretemix without sacrificing strength.

The carbon dioxide is contacted with the cement mix, e.g., hydrauliccement mix during mixing by any suitable route, such as over part or allof the surface of the mixing cement mix, e.g., hydraulic cement mix,under the surface of the cement mix, e.g., hydraulic cement mix, or anycombination thereof. In certain embodiments where concrete is mixed in afirst container and then introduced into a second container, such as ata ready-mix batching facility where concrete is first mixed in a mixerthen transferred to the drum of a ready-mix truck, carbon dioxide isintroduced into the second container prior to pre-mixed concrete beingintroduced into that container. Additionally or alternatively, theconcrete may be contacted with carbon dioxide as it is being transferredfrom the first mix container to the second container. The carbon dioxidemay be in any form as described herein, e.g., gas, solid, or a mix ofgas and solid. In certain embodiments, the carbon dioxide is introducedinto the second container as a solid, or a mixture of gas and solid; forexample, the carbon dioxide may be supplied in a conduit as liquidcarbon dioxide and on exiting an opening or orifice of the conduit, beconverted to solid and gaseous carbon dioxide, as described elsewhereherein; the stream of gaseous and solid carbon dioxide may be directedto the second container before introduction of the concrete, and/ordirected to the stream of concrete introduced into the second container.As it is advantageous to have a greater amount of solid carbon dioxideto avoid escape of gaseous carbon dioxide to the atmosphere, conditionsof the introduction may be adjusted to achieve a high ratio of solid togaseous carbon dioxide. Alternatively or additionally, carbon dioxidemay be introduced into the second container as dry ice, as describedelsewhere herein. The carbon dioxide in the second container is thencontacted with the pre-mixed concrete as it is poured into the secondcontainer and as the second container continues to mix the concrete.

For example, in a ready-mix operation, concrete is often mixed in amixer at the batching site and poured into the drums of ready-mix trucksfor transport to the job site. The concrete continues to mix in the drumof the ready-mix truck. Carbon dioxide can be introduced into the drumof the ready-mix truck, e.g., as gaseous and solid carbon dioxide formedfrom liquid carbon dioxide, or as solid dry ice, or a combinationthereof, prior to the concrete being poured from the mixer into thedrum. Additionally or alternatively, carbon dioxide may be directed tothe stream of concrete as it is being poured from the mixer to the drum.When the carbon dioxide is a mixture of gas and solid, e.g., producedfrom a liquid carbon dioxide, the stream of gas and solid may bedirected to contact the stream of concrete being poured from the mixer,as well as entering the drum of the ready-mix truck. Thus the stream ofsolid and gaseous carbon dioxide may be positioned in such a way as tointroduce carbon dioxide into the stream of concrete entering the drumof the truck, and also to introduce carbon dioxide into the drum itself.Carbon dioxide, e.g., solid carbon dioxide or a mixture of solid andgaseous carbon dioxide, may also be introduced into the drum of thetruck prior to the pouring of the concrete into the drum. It will beappreciated that any combination of the above approaches may be used inorder to contact the concrete in the drum of the truck with carbondioxide. Such approaches are especially useful with low doses of carbondioxide, such as doses no greater than 2%, or no greater than 1.5%, orno greater than 1% bwc, as described elsewhere herein.

In certain embodiments, the carbon dioxide is contacted with the cementmix, e.g., hydraulic cement mix during mixing by contact with thesurface of the mixing cement mix, e.g., hydraulic cement mix. Withoutbeing bound by theory, it is believed that the carbon dioxide contactedwith the surface of the cement mix, e.g., hydraulic cement mix dissolvesand/or reacts in the water, and is then subsumed beneath the surface bythe mixing process, which then exposes different cement mix, e.g.,cement mix, to be contacted, and that this process continues for as longas the wetted hydraulic cement is exposed to the carbon dioxide. It willbe appreciated that the process of dissolution and/or reaction maycontinue after the flow of carbon dioxide is halted, since carbondioxide will likely remain in the gas mixture in contact with the cementmix, e.g., hydraulic cement mix. In embodiments in which liquid carbondioxide is used to produce gaseous and solid carbon dioxide, the solidcarbon dioxide will sublimate and continue to deliver gaseous carbondioxide to the cement mix, e.g., hydraulic cement mix after the flow ofliquid carbon dioxide has ceased. This is particularly useful in readymix truck operations, where there may be insufficient time at thebatching facility to allow uptake of the desired amount of carbondioxide; the use of liquid carbon dioxide which converts to gaseous andsolid carbon dioxide allow more carbon dioxide to be delivered to themix even after the truck leaves the batching facility.

In particular, in a ready-mix operation, the concrete may be mixed in astationary mixer, then transferred to the drum of the ready-mix truck,or the components of the concrete may be delivered to the drum of theready-mix truck and the mixing of the components to provide concreteoccurs in the drum. In the former case, carbon dioxide may be deliveredto the stationary mixer, and in such a case, the delivery may be similaror identical to that used in, e.g., a precast operation, i.e., carbondioxide is delivered via a conduit which opens to the mixer and deliversthe carbon dioxide to the surface of the mixing concrete. The carbondioxide may be any form as described herein; in certain embodiments, thecarbon dioxide is delivered as liquid which, upon exiting the opening ofthe conduit, converts to a solid and a gas, as described herein. Furthercarbonation of the concrete may be achieved, if desired, by delivery ofadditional carbon dioxide to the drum of the ready mix truck after theconcrete is delivered to it. Alternatively, all carbon dioxide may bedelivered to the drum of the ready-mix truck; this will clearly be thecase if the mixing of the concrete occurs in the drum. In this case, adelivery system for carbon dioxide to the drum of the ready-mix truck isneeded.

The carbon dioxide can be delivered after the components of the concretemix are placed in the drum; for example, in some ready-mix operations,the truck is moved to a wash rack where it is washed down prior toleaving the yard. When such a delivery system is used, the positioningof the conduit for the carbon dioxide, also referred to as a wand orlance herein, so that the opening is in a certain position and attituderelative to the drum can be important; one aspect of some embodiments ofthe invention is positioning the wand, and/or apparatus for doing so, tofacilitate efficient mixing of the gaseous and solid carbon dioxide withthe cement mix as the drum rotates. Any suitable positioning methodand/or apparatus may be used to optimize the efficiency of uptake ofcarbon dioxide into the mixing cement as long as it positions the wandin a manner that provides efficient uptake of the carbon dioxide, forexample, by positioning the wand so that the opening is directed to apoint where a wave of concrete created by fins of the ready mix drumfolds over onto the mix; without being bound by theory it is thoughtthat the wave folding over the fin immediately subsumes the solid carbondioxide within the cement mix so that it releases gaseous carbon dioxideby sublimation into the mix rather than into the air, as it would do ifon the surface of the mix. One exemplary positioning is shown in FIG.134, where the wand is aimed at the second fin in the drum of the truck,on the bottom side of the fin. In a ready mix truck carrying a fullload, the opening of the wand may be very close to the surface of themixing concrete, as described below, to facilitate the directional flowof the carbon dioxide mix into the proper area. Part or all of the wandmay be made of flexible material so that if a fin or other part of thedrum hits the wand it flexes then returns to its original position.

In certain embodiments, the invention provides a system for positioninga carbon dioxide delivery conduit on a ready mix truck so that theopening of the conduit is directed to a certain position in the drum ofthe truck, for example, as described above. The conduit may delivergaseous carbon dioxide or a mixture of gaseous and solid carbon dioxidethrough the opening. In the latter case, the conduit is constructed ofmaterials that can withstand the liquid carbon dioxide carried by theconduit to the opening. The system can include a guide, which may bemounted on the truck, for example permanently mounted, or that may bepart of the lance assembly, that is configured to allow the reversiblepositioning of the conduit, for example, by providing a cylinder orholster into which the conduit can be inserted, so that the conduit ispositioned at the desired angle for delivery of the carbon dioxide to aparticular point, and a stop to ensure that the conduit is inserted sothat the opening is at the desired distance from the concrete. This ismerely exemplary and one of skill in the art will recognize that anynumber of positioning devices may be used, so long as the angle andposition of the opening relative to a desired point in the drum isobtained. The wand is positioned in the guide, for example, manually bythe driver, or automatically by an automated system that senses thepositions of the various components. A sensor may be tripped when thewand is positioned properly and a system controller may then begincarbon dioxide delivery, either at that time or after a desired delay.The controller can be configured so that if the conduit is notpositioned properly, e.g., the sensor does not send the signal, thedelivery will not start. The system may also be configured so that ifone or more events occur during before, during, or after delivery, analarm sounds and/or delivery is modulated, for example, stopped, or notinitiated. For example, an alarm can sound if the wand loses signal fromthe positioning sensor during injection, the pressure is greater than 25psi when both valves for delivery of gaseous and liquid carbon dioxideto the conduit is closed, e.g., when both are closed (which determinesif a valve sticks open), or if the next truck in the queue has not beeninitiated in a certain amount of time. Exemplary logic for a controllercan include:

If the wand loses signal during injection, an alarm light comes on and amessage can pop on a HMI, for example, a screen, informing an operatorthat the injection wand is disconnected and to reconnect and press Startbutton to continue. There can also be an indicator, e.g., a button thatindicates “Injection Complete” which would end that batch and recordwhat was actually injected vs the target. In a batching facility inwhich a plurality of different trucks are being batched, a systemcontroller may be configured to receive input regarding the identity ofeach truck at the carbon dioxide delivery site and select theappropriate action, e.g., delivery/no delivery, timing, flow, and amountof carbon dioxide delivered, and the like. For example, for entering atruck number that corresponds to the current truck being batched (signalbeing sent to plc), a dialog box can pop up when the system controllergets the signal from the customer PLC asking an operator to “Pleaseinput Identification Number” (e.g., a 1-10 digit number), alternatively,the truck identifier numbers can be in a predetermined order, e.g.,sequential. To choose the option, there may be a selector switch on themaintenance screen. Feedback may also be provided to an operator, e.g.,a batcher, showing relevant information for the batches run, such asIdentification Number, Time Batched, Time Injected, Dose Required andDose Injected, and the like. The units of the dose can be any suitableunits, for example either lbs or kgs depending on the units selected. A“spreadsheet” can be provided that shows all batches from the currentday (or makes the date selectable) so that the batcher can review it andscroll though, for example a printable spreadsheet.

In certain embodiments, carbon dioxide is added to the drum of aready-mix truck while the truck is positioned to receive the componentsof the concrete; this allows earlier contact of the carbon dioxide withthe concrete mix and also allows all components—concrete and carbondioxide—to be added at once, avoiding the necessity for the truckoperator to perform an additional step to add the carbon dioxide.Generally, in an operation where the components of the concrete areadded to the drum of the ready-mix truck for mixing, a flexible largeconduit, generally referred to as a loading boot, such as a rubber boot,is positioned to direct materials (cement, aggregate, etc.) from loadinghopper/bin into the concrete truck chute; this system minimizesspillage. See FIG. 135. In this case, a smaller conduit for delivery ofcarbon dioxide can be positioned within the larger conduit (boot) tomove with the boot and be configured to direct the carbon dioxide intothe drum of the ready-mix truck. Thus, an example another method andapparatus for positioning a wand for delivery of carbon dioxide to aready-mix truck is described in Example 42 and FIGS. 135 and 136. Inthis system, a flexible hose housed in a pipe, where the hose isextended through a loading boot and into a concrete truck's chute by theaction of an apparatus suitable for extending the hose, such as atelescopic air cylinder rod or a rotary device. One or more componentsof the apparatus may be suitably configured to direct the carbon dioxideto a desired location or area in the drum, such as by a bend in theapparatus.

In embodiments in which carbon dioxide is directed as a solid/gasmixture into a mixer, such as into a ready-mix truck or into astationary mixer, it may be desirable to modulate the flow, e.g., slowthe flow, so that the solid carbon dioxide particles can clump togetherinto larger particles before contacting the cement mix, e.g., hydrauliccement mix such as concrete, in the mixer. Without being bound bytheory, it is thought that by allowing larger conglomerations to form,the rate of sublimation is slowed and the released gaseous carbondioxide is more likely to be taken up by the cement mix rather thanescaping to the atmosphere.

One method modulating the flow of the solid/gas carbon dioxide mixtureis to expand the diameter of the conduit through which the solid/gasmixture flows, and/or to introduce a bend into the conduit. Both theincrease in diameter and the bend in the conduit serve to slow thevelocity; however, in certain embodiments only an increase in diameteris used; in certain embodiments, only a bend is used. Any suitablestep-up in size may be used, with or without a bend, so long as the rateof flow of the gas/solid carbon dioxide mix is slowed sufficiently toprovide the desired clumping of solid particles before contact with thecement mix; in general it is preferred that the velocity remain highenough that the solid carbon dioxide does not stick inside the conduit.

A larger diameter, with or without a bend, may also be used for aconduit used to deliver a gas/solid mixture of carbon dioxide to anon-stationary mixer, e.g., a ready-mix truck. The increase in diameterof the conduit may be any increase that produces the desired clumping ofthe solid carbon dioxide, preferably with no or very little buildup ofsolid carbon dioxide in the conduit.

It will be appreciated that other systems of positioning a conduit fordelivery of carbon dioxide to a ready-mix truck may be used, such assystems wherein the conduit, or lance, is attached to a stand and ispositioned into the drum of the truck without being temporarily attachedto the truck. Such systems are included in embodiments of the invention.For descriptions of exemplary systems, see, e.g., U.S. PatentApplication Publication No. 2014/0216303, and U.S. Pat. No. 8,235,576.

In embodiments in which carbon dioxide is contacted with the surface ofthe cement mix, e.g., hydraulic cement mix, the flow of carbon dioxidemay be directed from an opening or plurality of openings (e.g., manifoldor conduit opening) that is at least 5, 10, 20, 30, 40, 50, 60, 70, 80,90, or 100 cm from the surface of the cement mix, e.g., hydraulic cementmix during carbon dioxide flow, on average, given that the surface ofthe mix will move with mixing, and/or not more than 10, 20, 30, 40, 50,60, 70, 80, 90, 100, 120, 140, 170, or 200 cm from the surface of thecement mix, e.g., hydraulic cement mix during carbon dioxide flow, onaverage. In certain embodiments, the opening is 5-100 cm from thesurface, on average, such as 5-60 cm, for example 5-40 cm.

Other methods of increasing carbon dioxide delivery, such as usingcarbon dioxide-charged water in the mix, may also be used. In addition,or alternatively, solid carbon dioxide, i.e., dry ice, may be useddirectly by addition to the concrete mix. This allows for controlleddelivery as the dry ice sublimates, as described. For example, dry icemay be added to a cement mix in a ready mix truck. The amount of dry iceadded may be enough to provide a dose of 0.01-5% carbon dioxide bwc, forexample, 0.01-1%, or 0.01-0.5%, or 0.01-0.2%, or 0.1-2% or 0.1-1%, or0.2-3%, or 0.5-3%. The dry ice may be added in one or more batches. Theshape of the dry ice may be selected depending on, e.g., the speed ofgaseous carbon dioxide delivery desired; for example, if rapid deliveryis desired, the dry ice may be added as small pellets, thus increasingsurface/volume ratio for carbon dioxide sublimation, or if a slowerdelivery is desired, the dry ice may be added as a larger mass, e.g.,slab, with a correspondingly smaller surface/volume ratio and slowersublimation, or any combination of shapes and masses to achieve thedesired dose of carbon dioxide and rate of delivery. The dry ice may beadded at any convenient stage in mixing, for example, at the start ofmixing or within 5 or 10 minutes of the start of mixing, or later in themixing, for example, as a ready mix truck approaches a job site or thetime of delivery of its concrete load. In addition, solid carbon dioxidemay be added before or after a first, second, or third addition of waterwhere water addition to the concrete mix is divided into two or moredoses. Mixing speed for the concrete mix may also be modulated toachieve a desired rate of dosing or other desired results. For example,in certain embodiments, the invention provides a method for deliveringcarbon dioxide to concrete mixing in a ready mix truck by adding solidcarbon dioxide to the concrete mix during the mixing, where at least 20,30, 40, 50, 60, 70, 80, 90, 95, or 99% of the carbon dioxide deliveredto the concrete is added in the form of solid carbon dioxide.

In embodiments in which the carbon dioxide is contacted under thesurface of the cement mix, e.g., hydraulic cement mix, any suitableroute of providing the carbon dioxide may be used. In some embodiments,the flow of carbon dioxide may be both under the surface and over thesurface, either by use of two different openings or plurality ofopenings or by movement of the openings relative to the mix, e.g., underthe surface at one stage and over the surface at another, which may beuseful to prevent clogging of the openings.

The carbon dioxide may be contacted with the cement mix, e.g., hydrauliccement mix such that it is present during mixing by any suitable systemor apparatus. In certain embodiments, gaseous or liquid carbon dioxideis supplied via one or more conduits that contain one or more openingspositioned to supply the carbon dioxide to the surface of the mixingcement mix, e.g., hydraulic cement mix. The conduit and opening may beas simple as a tube, e.g., a flexible tube with an open end. The conduitmay be sufficiently flexible so as to allow for movement of variouscomponents of the cement mix, e.g., hydraulic cement mixing apparatus,the conduit opening, and the like, and/or sufficiently flexible to beadded to an existing system as a retrofit. On the other hand, theconduit may be sufficiently rigid, or tied-off, or both, to insure thatit does not interfere with any moving part of the cement mix, e.g.,hydraulic cement mixing apparatus. In certain embodiments, part of theconduit can be used for supplying other ingredients to the cement mix,e.g., water, and configured such that either the other ingredient orcarbon dioxide flows through the conduit, e.g., by a T-junction.

In certain embodiments, the carbon dioxide exits the conduit or conduitsvia one or more manifolds comprising a plurality of openings. Theopening or openings may be positioned to reduce or eliminate clogging ofthe opening with the cement mix, e.g., hydraulic cement mix. Themanifold is generally connected via the conduit to at least one fluid(gas or liquid) supply valve, which governs flow of pressurized fluidbetween a carbon dioxide source, e.g. a pressurized gas or liquidsupply, and the manifold. In some embodiments, the fluid supply valvemay include one or more gate valves that permit the incorporation ofcalibration equipment, e.g., one or more mass flow meters.

The mass of carbon dioxide provided to the cement mix, e.g., hydrauliccement mix via the conduit or conduits may be controlled by a mass flowcontroller, which can modulate the fluid supply valve, e.g., close thevalve to cease supply of carbon dioxide fluid (liquid or gas).

Carbon dioxide may also be delivered to the cement mix, e.g., hydrauliccement mix as part of the mix water, i.e., dissolved in some or all ofthe mix water. Methods of charging water with carbon dioxide arewell-known, such as the use of technology available in the sodaindustry. Some or all of the carbon dioxide to be used may be deliveredthis way. The mix water may be charged to any desired concentration ofcarbon dioxide achievable with the available technology, such as atleast 1, 2, 4, 6, 8, 10, 12, 14, or 16 g of carbon dioxide/L of water,and/or not more than 2, 4, 6, 8, 10, 12, 14, 18, 20, 22, or 24 g ofcarbon dioxide/L of water, for example 1-12, 2-12, 1-10, 2-10, 4-12,4-10, 6-12, 6-10, 8-12, or 8-10 g of carbon dioxide/L of water. It willbe appreciated that the amount of carbon dioxide dissolved in the mixwater is a function of the pressure of the carbon dioxide and thetemperature of the mix water; at lower temperatures, far more carbondioxide can be dissolved than at higher temperatures. Without beingbound by theory, it is thought that the mix water so charged contactsthe cement mix, e.g., hydraulic cement mix and the carbon dioxidecontained therein reacts very quickly with components of the cement mix,e.g., hydraulic cement mix, leaving the water available to dissolveadditional carbon dioxide that may be added to the system, e.g., ingaseous form.

In certain embodiments, a cement mix such as a concrete mix iscarbonated with carbon dioxide supplied as carbonated water, forexample, in the drum of a ready mix truck. The carbonated water servesas a portion of the total mix water for the particular mix. Thecarbonated water can provide at least 1, 5, 10, 15, 20, 25, 30, 35, 40,50, 60, 70, 80, or 90% of the total mix water, and/or no more than 10,20, 30, 40, 50, 60, 70, 80, 90, 95, or 100% of the mix water. Thecarbonated water may be added at the start of mixing of the cement mix,or it may be added after the start of mixing, i.e., after a firstaddition of water to wet the cement mix. It can be added as one batch orin stages, for example, as 2, 3, 4, 5 or more than 5 batches. Thebatches may be equal in volume or different volumes, and have the samecarbonation or different carbonations. In certain embodiments, thecarbonated water is less than 100% of the total mix water, for example,less than 80%, or less than 70%, or less than 60%, or less than 50%. Incertain of these embodiments, embodiments, non-carbonated water is firstadded to the mix, and the cement mix, e.g., concrete, is allowed to mixfor a certain period before carbonated water is added, for example, forat least 5, 10, 15, 20, 30, 40, or 50 seconds, or at least 1, 2, 3, 4,5, 6, 8, 10, 15, 20, 25, 30, 40, 50, or 60 minutes before addition ofthe carbonated water, and/or not more than 10, 15, 20, 30, 40, or 50seconds, or 1, 2, 3, 4, 5, 6, 8, 10, 15, 20, 25, 30, 40, 50, 60, 90,120, 240, or 360 minutes before addition of carbonated water. In certainembodiments, the delay before carbonated water is added to the mix isbetween 10 seconds and 5 minutes, for example, between 20 seconds and 40minutes, such as between 30 seconds and 3 minutes. See Example 38. Theflow rate of the carbonated water may be adjusted so that a certainduration is required for complete addition, such as a duration of atleast 10, 20, 30, 40, or 50 seconds, or at least 1, 2, 3, 4, 5, 6, 7, 8,9, 10, 12, 15, 20, or 30 minutes, and/or not more than 10, 20, 30, 40,or 50 seconds, or not more than 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 15,20, or 30 minutes. In certain embodiments, the duration of addition ofcarbonated water is between 30 seconds and 8 minutes, for example,between 30 seconds and 6 minutes, such as between 30 second and 4minutes. See Example 38. The carbonated water may contribute all of thecarbon dioxide used to carbonate a cement mix, e.g., concrete(neglecting atmospheric carbon dioxide); this is especially true forlow-dose carbonation, for example, carbonation with a dose of carbondioxide of less than 1.5% bwc, or less than 1.0% bwc, or less than 0.8%bwc. The carbonated water may contribute part or all of the carbondioxide used to carbonate a cement mix, e.g., concrete, such as not morethan 10, 20, 30, 40, 50, 60, 70, 80, 90, 95, or 100% of the carbondioxide and/or at least 5, 10, 20, 30, 40, 50, 60, 70, 80, 90, or 95% ofthe carbon dioxide. In certain embodiments, the remaining carbon dioxideis supplied as a gas. In certain embodiments, the remaining carbondioxide is supplied as a solid. In certain embodiments, the remainingcarbon dioxide is supplied as a mixture of a gas and a solid, forexample, carbon dioxide delivered to an orifice directed into the mixerin liquid form, which becomes gas and solid when passing through theorifice. The exact mix of carbonated water and other carbon dioxidesource will be determined based on the dose of carbon dioxide to bedelivered and other factors, such as delivery time, temperature (lowertemperatures allow greater carbon dioxide delivery via carbonatedwater), and the like. The carbonated water may be produced by anysuitable method, as described herein, and may be delivered to the mixer,e.g., the ready mix truck, via the normal water line or via a dedicatedline. In certain embodiments, some or all of the carbonated water isproduced from process water that is produced during, e.g., a ready mixoperation, such as carbonated wash water that has been filtered, orunfiltered carbonated wash water, or a combination thereof. The washwater may be carbonated by any suitable method. See Example 39. Thecarbonated wash water can provide at least 1, 5, 10, 15, 20, 25, 30, 35,40, 50, 60, 70, 80, or 90% of the total carbonated mix water, and/or nomore than 10, 20, 30, 40, 50, 60, 70, 80, 90, 95, or 100% of the totalcarbonated mix water. In certain embodiments carbonated water isdelivered to the mix at the batch site and/or during transportation, andan optional dose is delivered at the job site, depending on thecharacteristics of the mix measured at the job site. The use ofcarbonated water can allow for very high efficiencies of carbon dioxideuptake, as well as precise control of dosage, so that highly efficientand reproducible carbon dioxide dosing can be achieved. In certainembodiments in which carbonated mix water is used, the efficiency ofcarbonation can be greater than 60, 70, 80, 90, or even 95%, even whenoperating in mixers, such as ready mix drums, which are open to theatmosphere.

The carbon dioxide is supplied from a source of carbon dioxide, such as,in the case of gaseous carbon dioxide, a pressurized tank filled withcarbon dioxide-rich gas, and a pressure regulator. The tank may bere-filled when near empty, or kept filled by a compressor. The regulatormay reduce the pressure in the tank to a maximum feed pressure. Themaximum feed pressure may be above atmospheric, but below supercriticalgas flow pressure. The feed pressure may be, for example, in a rangefrom 120 to 875 kPa. A pressure relief valve may be added to protect thecarbon dioxide source components. The carbon dioxide supplied by thecarbon dioxide source may be about room temperature, or it may bechilled or heated as desired. In certain embodiments, some or all of thecarbon dioxide is supplied as a liquid. In some cases the liquid isconverted to gas before delivery to the mixer; in other cases, theremains a liquid in storage and movement to the mixer, and when releasedat the mixer forms a mixture comprising solid and gaseous carbondioxide. In the latter case, one or more pressure sensors may be used;e.g., for the nozzle system to control dry ice formation between thenozzle and solenoid as well as to confirm pre-solenoid pressure ismaintained to ensure the line remains liquid.

Carbon dioxide may be introduced to the mixer such that it contacts thehydraulic cement mix before, during, or after addition of water, or anycombination thereof, so long as it is present during some portion of themixing of some or all of the cement mix, e.g., hydraulic cement mix. Incertain embodiments, the carbon dioxide is introduced during a certainstage or stages of mixing. In certain embodiments, the carbon dioxide isintroduced to a cement mix, e.g., hydraulic cement mix during mixing atone stage only. In certain embodiments, the carbon dioxide is introducedduring one stage of water addition, followed by a second stage of wateraddition. In certain embodiments, the carbon dioxide is introduced toone portion of cement mix, e.g., hydraulic cement mix, followed byaddition of one or more additional portions of cement mix, e.g.,hydraulic cement mix.

In certain embodiments, the carbon dioxide is introduced into a firststage of mixing of water in the cement mix, e.g., hydraulic cement mix,then, after this stage, additional water is added without carbondioxide. For example, water may be added to a cement mix, e.g.,hydraulic cement mix, e.g., a Portland cement mix, until a desired w/cratio is achieved, then carbon dioxide may be contacted during mixing ofthe cement mix, e.g., hydraulic cement mix for a certain time at acertain flow rate or rates (or as directed by feedback, describedfurther herein), then after carbon dioxide flow has stopped, additionalwater may be added in one or more additional stages to reach a desiredw/c content, or a desired flowability, in the cement mix, e.g.,hydraulic cement mix. The cement mixes contain aggregates, and it willbe appreciated that the available aggregate may already have a certainwater content and that little or no additional water need be added toachieve the desired w/c ratio for the first stage and that, in someenvironments, it may not be possible to achieve the desired w/c ratiobecause aggregate may be too wet, in which case the closest w/c ratio tothe optimum is achieved. In certain embodiments, the w/c ratio for thefirst stage is less than 0.5, or less than 0.4, or less than 0.3, orless than 0.2, or less than 0.18, or less than 0.16, or less than 0.14,or less than 0.12, or less than 0.10, or less than 0.08, or less than0.06. In certain embodiments, the w/c ratio for the first stage is lessthan 0.4. In certain embodiments, the w/c ratio for the first stage isless than 0.3. In certain embodiments, the w/c ratio for the first stageis less than 0.2. In certain embodiments, the w/c ratio for the firststage is less than 0.18. In certain embodiments, the w/c ratio for thefirst stage is less than 0.14. In certain embodiments, the w/c ratio forthe first stage is 0.04-0.5, or 0.04-0.4, or 0.04-0.3, or 0.04-0.2, or0.04-0.18, or 0.04-0.16, or 0.04-0.14, or 0.04-0.12, or 0.04-0.10, or0.04-0.08. In certain embodiments, the w/c ratio for the first stage is0.06-0.5, or 0.06-0.4, or 0.06-0.3, or 0.06-0.24, or 0.06-0.22, or0.06-0.2, or 0.06-0.18, or 0.06-0.16, or 0.06-0.14, or 0.06-0.12, or0.06-0.10, or 0.06-0.08. In certain embodiments, the w/c ratio for thefirst stage is 0.08-0.5, or 0.08-0.4, or 0.08-0.3, or 0.08-0.24, or0.08-0.22, or 0.08-0.2, or 0.08-0.18, or 0.08-0.16, or 0.08-0.14, or0.08-0.12, or 0.08-0.10. In certain embodiments, the w/c ratio for thefirst stage is 0.06-0.3. In certain embodiments, the w/c ratio for thefirst stage is 0.06-0.2. In certain embodiments, the w/c ratio for thefirst stage is 0.08-0.2. Addition of additional water in subsequentstages to the first stage, when, in general, no further carbon dioxideis introduced, may be done to achieve a certain final w/c ratio, or toachieve a certain flowability. For example, for a ready-mix truck, acertain amount of water is added to the mixture at the ready-mixproduction site, then further water may be added at the work site toachieve proper flowability at the work site. Flowability may be measuredby any suitable method, for example, the well-known slump test.

In some embodiments, carbon dioxide is added during mixing to a portionof a cement mix, e.g., hydraulic cement mix in one stage, thenadditional portions of materials, e.g., further cement mix, e.g.,hydraulic cement mix, are added in one or more additional stages.

The carbon dioxide, e.g., gaseous carbon dioxide or liquid carbondioxide, is introduced in the mixing cement mix, e.g., hydraulic cementmix, for example, in the first stage of mixing, at a certain flow rateand for a certain duration in order to achieve a total carbon dioxideexposure. The flow rate and duration will depend on, e.g., the purity ofthe carbon dioxide gas, the total batch size for the cement mix, e.g.,hydraulic cement mix and the desired level of carbonation of the mix. Ametering system and adjustable valve or valves in the one or moreconduits may be used to monitor and adjust flow rates. In some cases,the duration of carbon dioxide flow to provide exposure is at or below amaximum time, such as at or below 100, 50, 20, 15, 10, 8, 5, 4, 3, 2, orone minute. In certain embodiments, the duration of carbon dioxide flowis less than or equal to 5 minutes. In certain embodiments, the durationof carbon dioxide flow is less than or equal to 4 minutes. In certainembodiments, the duration of carbon dioxide flow is less than or equalto 3 minutes. In certain embodiments, the duration of carbon dioxideflow is less than or equal to 2 minutes. In certain embodiments, theduration of carbon dioxide flow is less than or equal to 1 minutes. Insome cases, the duration of carbon dioxide flow to provide exposure iswithin a range of times, such as 0.5-20 min, or 0.5-15 min, or 0.5-10min, or 0.5-8 min, or 0.5-5 min, or 0.5-4 min, or 0.5-3 min, or 0.5-2min, or 0.5-1 min, or 1-20 min, or 1-15 min, or 1-10 min, or 1-8 min, or1-5 min, or 1-4 min, or 1-3 min, or 1-2 min. In certain embodiments, theduration of carbon dioxide flow is 0.5-5 min. In certain embodiments,the duration of carbon dioxide flow is 0.5-4 min. In certainembodiments, the duration of carbon dioxide flow is 0.5-3 min. Incertain embodiments, the duration of carbon dioxide flow is 1-5 min. Incertain embodiments, the duration of carbon dioxide flow is 1-4 min. Incertain embodiments, the duration of carbon dioxide flow is 1-3 min. Incertain embodiments, the duration of carbon dioxide flow is 1-2 min.

The flow rate and duration of flow may be set or adjusted to achieve adesired level of carbonation, as measured by weight of cement (bwc). Itwill be appreciated that the precise level of carbonation will depend onthe characteristics of a given mix and mix operation. In certainembodiments, the level of carbonation is more than 0.5, 1, 2, 3, 4, 5,6, 7, 8, 9, or 10% bwc. In certain embodiments, the level of carbonationis more than 1% by weight. In certain embodiments, the level ofcarbonation is more than 2% bwc. In certain embodiments, the level ofcarbonation is more than 3% bwc. In certain embodiments, the level ofcarbonation is more than 4% bwc. In certain embodiments, the level ofcarbonation is more than 5% bwc. In certain embodiments, the level ofcarbonation is more than 6% bwc. In certain embodiments, the level ofcarbonation is 1-20%, or 1-15%, or 1-10%, or 1-8%, or 1-6%, or 1-5%, or1-4%, or 1-3%, or 1-2%, or 2-20%, or 2-15%, or 2-10%, or 2-8%, or 2-6%,or 2-5%, or 2-4%, or 2-3%, or 0.5-20%, or 0.5-15%, or 0.5-10%, or0.5-8%, or 0.5-6%, or 0.5-5%, or 0.5-4%, or 0.5-3%, or 0.5-2%. Incertain embodiments, the level of carbonation is 0.5-3%. In certainembodiments, the level of carbonation is 0.5-2%. In certain embodiments,the level of carbonation is 1-6%. In certain embodiments, the level ofcarbonation is 1-4%. In certain embodiments, the level of carbonation is2-8%. In certain embodiments, the level of carbonation is 2-6%. Incertain embodiments, the level of carbonation is 2-4%. In certainembodiments, the level of carbonation is 3-10%. In certain embodiments,the level of carbonation is 3-8%. In certain embodiments, the level ofcarbonation is 3-6%. In certain embodiments, the level of carbonation is4-10%. In certain embodiments, the level of carbonation is 4-8%. Incertain embodiments, the level of carbonation is 4-6%. In certainembodiments, the level of carbonation is 5-10%. In certain embodiments,the level of carbonation is 5-8%. In certain embodiments, the level ofcarbonation is 5-6%. The level of carbonation may be ascertained by anysuitable method, such as by the standard combustion analysis method,e.g. heating sample and quantifying the composition of the off gas. Aninstrument such as the Eltra CS-800 (KR Analytical, Cheshire, UK), orinstrument from LECO (LECO Corporation, St. Joseph, Mich.) may be used.

It will be appreciated that the level of carbonation also depends on theefficiency of carbonation, and that inevitably some of the carbondioxide delivered to the mixing cement mix will be lost to theatmosphere; thus, the actual amount of carbon dioxide delivered can beadjusted based on the expected efficiency of carbonation. Thus for allthe desired levels of carbonation as listed, an appropriate factor maybe added to determine the amount of carbon dioxide that is to bedelivered as a dose to the cement mix; e.g., if the expected efficiencyis 50% and the desired carbonation level is 1% bwc, then a dose of 2%bwc would be delivered to the mix. Appropriate doses may be calculatedfor desired carbonations at an efficiency of 5, 10, 20, 30, 40, 50, 60,65, 70, 75, 80, 85, 90, 95, 96, 97, 98, or 99%.

Low Dose Carbonation

In certain embodiments, a relatively low level of carbonation is used,e.g., a level of carbonation below 1%, 0.8%, 0.7%, 0.6%, 0.5%, 0.4%,0.3%, 0.2%, 0.1%, or 0.05% bwc. It has been found that certainproperties, e.g., early strength development and set, may be acceleratedin cement mixes, such as hydraulic cement mixes, that are exposed torelatively low levels of carbon dioxide during mixing. It is possiblethat, in some cases, the exposure may be low enough that the degree ofcarbonation is not measurably above that of a similar cement mix thathas not been exposed to carbon dioxide; nonetheless, the exposure maylead to the desired enhanced properties. Thus, in certain embodiments,the mixing cement mix is exposed to a certain relatively low dose ofcarbon dioxide (in some cases regardless of final carbonation value); inthis sense, carbon dioxide is used like an admixture whose finalconcentration in the cement mix is not important but rather its effectson the properties of the mix. In certain embodiments, the mix may beexposed to a dose of carbon dioxide of not more than 1.5%, 1.2%, 1%,0.8%, 0.7%, 0.6%, 0.5%, 0.4%, 0.3%, 0.2%, 0.1%, or 0.05% bwc and/or atleast 0.01, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, or1.2% bwc, such as a dose of 0.01-1.5%, 0.01-1.2%, 0.01-1%, 0.01-0.8%,0.01-0.6%, 0.01-0.5%, 0.01-0.4%, 0.01-0.3%, 0.01-0.2%, or 0.01-0.1% bwc,or a dose of 0.02-1.5%, 0.02-1.2%, 0.02-1%, 0.02-0.8%, 0.02-0.6%,0.02-0.5%, 0.02-0.4%, 0.02-0.3%, 0.02-0.2%, or 0.02-0.1% bwc, or a doseof 0.04-1.5%, 0.04-1.2%, 0.04-1%, 0.04-0.8%, 0.04-0.6%, 0.04-0.5%,0.04-0.4%, 0.04-0.3%, 0.04-0.2%, or 0.04-0.1% bwc, or a dose of0.06-1.5%, 0.06-1.2%, 0.06-1%, 0.06-0.8%, 0.06-0.6%, 0.06-0.5%,0.06-0.4%, 0.06-0.3%, 0.06-0.2%, or 0.06-0.1% bwc, or a dose of0.1-1.5%, 0.1-1.2%, 0.1-1%, 0.1-0.8%, 0.1-0.6%, 0.1-0.5%, 0.1-0.4%,0.1-0.3%, or 0.1-0.2% bwc. The choice of exposure level will depend onfactors such as efficiency of carbonation in the process being used,degree of modulation of one or more properties desired (e.g., earlystrength development or early set), type of operation (e.g., dry castvs. wet cast), and type of cement, as different types of cement mayproduce mixes with different degrees of modulation with a given carbondioxide exposure. If an unfamiliar cement or mix type is being used,preliminary work may be done to find one or more suitable carbon dioxidedoses to produce the desired results. Especially in the case ofaccelerated strength and/or set development, the use of an appropriatedose of carbon dioxide can allow work to progress faster, e.g., verticalpours may move upward more quickly, surfaces may be finished earlier,molds removed earlier, and the like.

Tailoring Carbonation to Mix and Conditions at Site

In all dosing settings, for example, in low dose, the dose chosen for agiven mix as well as dosing conditions, for example, to produce adesired increase in early strength or set, or to produce an optimalincrease in early strength or set, can be dependent on the mix andespecially on the cement used in the mix, as well as conditions in thefield where dosing and use actually occur. Cements used in mixes aregenerally produced locally and vary from one geographic location toanother, and the particular chemistry of a cement can determine whetheror not it will benefit from carbonation, as well as optimal dosingparameters, such as overall dose, time to add carbon dioxide, rate ofaddition, and the like. Other components of a particular mix, e.g. SCMssuch as fly ash or slag, may also provide one or more reactive speciesthat also influence carbonation. See, e.g., Example 45.

In certain embodiments, the invention provides methods for determiningwhether or not to carbonate a given cement mix, and/or to determine alevel of carbonation and/or dose of carbon dioxide and/or dosingconditions to achieve a desired result from carbonation of a cement mix,e.g., early strength development, or strength development in aparticular time frame, reduced amount of cement required, or the like.The determination may be made by predictions for a given mix, e.g.,based on the chemistry of the components, or testing, or a combinationthereof. In testing, any suitable characteristic or combination ofcharacteristics may be monitored in the testing, such as strength,flowability, and other characteristics that are important for theparticular batch design being tested. In certain embodiments theinvention provides a method of carbonating a cement mix, e.g., concrete,during mixing, where carbon dioxide is added to the mix at a certaindose or range of doses, where the certain dose or range of doses isdetermined by testing one or more components of the mix, for example,the concrete, to determine a dose or a range of doses that producesoptimal or desired increase in early strength and/or set.

The composition of the cement mix for testing can be any suitablecomposition, for example, as simple as cement and water, or a mortaralso including fine aggregate, e.g., sand, as well as optionaladditional components, such as admixtures and the like. See Examples forcompositions used in testing. In certain embodiments the concrete mix tobe used in a given operation is tested.

Carbonation of the test cement mix can be achieved by any of the methodsdescribed herein, for example by delivery of carbon dioxide to thecement mix under controlled conditions to achieve a certain dose ofcarbon dioxide to the mix. In certain embodiments, the carbonation isachieved by using a bicarbonate solution, rather than carbon dioxide. Itis thought that essentially all of the bicarbonate delivered to aconcrete mix will be converted to carbonate so it is possible to controlthe exact level of carbonation of the mix achieved, and thus to firstdetermine a desired level of carbonation, e.g., by testing a pluralityof levels of carbonation to find the level or range of levels thatproduces the desired effect or effects. See, e.g., Example 37.

No matter what method of carbonation is used, if pre-testing is used todetermine a dose or range of doses, in general a plurality of tests isconducted, i.e., using at least two, or at least three, or at least fourdifferent doses of carbon dioxide. For low-dose carbon dioxide delivery,the doses may all be below 1.5%, or 1.2%, or 1.0%, or 0.8%, or 0.6%carbon dioxide bwc. A dose or range of doses to be used in the field isdetermined from one or more test results from the test mixes, forexample, calorimetry results, as described herein, and/or compressivestrength results, and/or set results, and/or slump results. Methods ofmeasuring strength, set, slump, and other characteristics of concretemixes are well-known in the art and described, e.g., in the appropriateASTM testing protocols. In certain embodiments, the test mix comprisesthe type of cement to be used in the concrete mix, and water; additionalcomponents may include one or more aggregates, admixtures, SCM, and anyother suitable component, for example, as will be used in the concretemix; generally, components are used at or near the proportion that willbe used in the concrete mix. In certain embodiments, the test mixcomprises all the components to be used in the concrete mix, in the sameproportions as will be used.

The focus can then shift to consistently achieving the desired level ofcarbonation under the conditions in which the carbon dioxide willactually be delivered to the cement mix to be used in the field. Forexample, in a ready mix operation, a certain efficiency may be achieved,e.g., by using techniques described herein, so that the dose of carbondioxide actually delivered may be adjusted according to the efficiencyof carbonation. Factors such as the likely temperature at the batchingfacility and/or job site can also affect carbonation and can also betaken into account. See Example 40. It will be appreciated that themethods and composition of the invention can be used to allow concretemixes to be used at temperatures lower than they would otherwise be ableto be used by virtue of the effects of carbonation on early strengthdevelopment, for example, at a temperature at least 1, 2, 3, 4, 5, 6, 7,8, 9, or 10° C. below the temperature at which a non-carbonated mix ofthe same or substantially the same design could be used.

Other factors that can affect efficiency of carbonation and/or theeffect of carbonates can include factors such as shear rate of mixing,timing after water is added to the mix at which the carbon dioxide isadded to the mix, e.g., delayed addition, and temperature as describedabove. Without being bound by theory, it is thought that these factorscan affect the formation of nano-sized calcium carbonate, which can inturn affect the resulting influence of calcium carbonate formation on,e.g., strength development and/or other characteristics of the cementmix. A high shear rate can prevent aggregation of particles and thuspromotes formation of nanoparticles. Delaying addition of carbon dioxidecan allow calcium to come into solution and allow solution chemistry todevelop.

In certain embodiments, the invention provides methods for determiningwhether or not to carbonate a given cement mix, and/or to determine alevel of carbonation and/or dose of carbon dioxide and/or dosingconditions to achieve a desired result from carbonation of a cement mix,e.g., early strength development, or strength development in aparticular time frame, or reduced amount of cement needed in the mix, orthe like. is determined, in whole or in part, from the chemistry of thecement to be used in the cement mix. In certain embodiments, one or moreof free CaO, total CaO, alkali content, loss on ignition, one or moreoxides, ratio of calcium to silica, fineness, iron content, orcombinations thereof can be used to determine a dose or range of dosesfor carbonation, and/or dosing conditions for a particular cement mix.

It will be appreciated that, in the case of low dose carbonation, acarbonation value may not be able to be determined, and that in allcases strength tests can require multiple samples and days to weeks tocomplete. Thus in some embodiments, a predetermined dose of carbondioxide is determined using an alternative marker, such as isothermalcalorimetry. Heat release during hydration is related to two somewhatoverlapping peaks. The main heat release is related to the hydration ofsilicates, while a second heat release, observed as a hump on thedownslope of the silicate peak, is associated with the hydration of thealuminates. Isothermal calorimetry testing is easy to carry out inmortar or even cement paste with very minimal sample preparationcompared to the making of concrete samples, thus allowing for a rapidand convenient method of determining an optimal CO₂ dose and timing fora given cement, by testing a range of doses and delivery times. Theresults obtained are either in the form of heat flow rate over time(also referred to as power vs. time herein), which describes the rate ofcement hydration, or in the form of heat of hydration over time, whichis the integrated heat flow rate (also referred to as energy vs. timeherein). See, e.g., Example 30, which describes several different dosesof carbon dioxide added to concrete in the drum of a ready mix truck, intrials conducted on two separate days. FIGS. 81-85 show the absolute andrelative compressive strengths of samples from the different doses ofcarbon dioxide, at different time points, for the first day; it can beseen that as carbon dioxide dose increased, strength at all time pointsgenerally increased. The isothermal calorimetry curves shown in FIGS.86A and 86B mirror this, with the highest dose of carbon dioxide causingthe greatest shift in the curve, and second and third highest dosesgiving the second and third greatest shifts in the curves. Similarresults can be seen in other Examples, e.g., Example 30 and others.

Cements that are suitable for carbonation—with respect to acceleratedset and/or early strength development—can be readily identified, and/ora dose or doses selected, as well as time of dosing, from theisocalorimetry curves using any suitable procedure, such as a procedurein which a cement paste, mortar, or concrete is produced using thecement being tested. Admixtures may also be tested, either separately oras part of an overall protocol, to determine their effects onworkability and other desired characteristics, as well as optimal doses.

An exemplary procedure is as follows:

-   -   1. Prepare a “control-control” sample with no carbonation and no        admixture.    -   2. Prepare a control sample with no carbonation and admixture        for desired “control” workability, if admixture is used.    -   3. CO₂ uptake dosage ramp: Prepare one or more carbonated        samples with incrementally higher CO₂ dosages. A chemical        admixture may be included to restore workability, and/or to        enhance early strength development. Admixtures themselves may be        optimized by preparing carbonated samples with fixed CO2 dose        and variable admixture type and dosing (e.g. compare gluconate        vs fructose, before and after CO₂, with dispersant)    -   4. Plot the power/heat flow rate for each mix as a function of        time    -   5. Plot the integrated power/heat flow rate, energy/heat of        hydration, as a function of time, excluding the initial exotherm        occurring prior to the onset of the main hydration peak in the        heat flow plot. See ASTM C 1679 for the definition of the main        hydration peak.    -   The following features from the heat flow rate plot and the heat        of hydration are indicative of accelerated development of set or        early strength:        -   a) If the onset of the main hydration peak in the power/heat            flow rate plot occurs sooner for a carbonated mix then this            indicates accelerated set and early strength development        -   b) If the energy/heat of hydration for a carbonated mix            exceeds the heat of hydration for the control mix then this            indicates a continuously higher early strength during the            time that the heat of hydration stays above the control.        -   c) If the results from several different CO₂ dosages and/or            admixture dosages are obtained then one can use the results            not only to identify cements that responds favorably to            carbonation, but also to “dial-in” the optimum CO₂ uptake            and admixture dose for said cement with respect to the            development of mechanical properties at early age.

The information obtained is especially useful for evaluating cementssuitable for carbonation in pre-cast applications and any otherapplication where accelerated set and early strength is of value.Optionally, samples can be prepared for testing of strength development,to verify the calorimetry results. In general, admixtures are used torestore workability in order to generate well compacted samples withreliable strength data. Doses for carbon dioxide and, optionally, typesand doses of admixture, for a given mix may thus be determined rapidlyand efficiently, then the dose determined in the testing is used in theactual carbonation.

In low dose carbonation, as in all cement mix, e.g., concrete,carbonation, various factors may be manipulated to produce optimal ordesired results. These include one or more of: time after beginning ofmixing at which carbon dioxide is applied; number of doses of carbondioxide; rate at which carbon dioxide is supplied to the mixing chamber;form of the carbon dioxide (gas, solid, and/or dissolved in water); andthe like. Mixing is said to have commenced upon addition of the firstaliquot of water to the cement-containing mix. It will be appreciatedthat in certain instances, components of a concrete mix, e.g.,aggregate, may be wet and that “the first mix water” may be the water onthe aggregate. Carbon dioxide can be supplied to a mix before the firstaddition of water, for example by flooding a chamber or head space withcarbon dioxide before water addition, but in this case the applicationof carbon dioxide is considered to occur when the first water is added,since virtually no reaction will occur until the carbon dioxidedissolves in the mix water.

In certain operations, e.g., precast operations, there is littleflexibility as to when carbon dioxide is added to the mixing concrete,as mix times are generally very short and the concrete is typically usedvery quickly after mixing. In these operations, addition of carbondioxide to the mixing concrete generally begins simultaneously with thecommencement of mixing or within seconds or, at most, minutes of thecommencement of mixing. In other operations, e.g., ready-mix operations,there are several times at which carbon dioxide can be added to themixing concrete. Carbon dioxide can be added during batching, which canoccur either in a fixed mixer or in the drum of the ready-mix truck; inthis case, the carbon dioxide contacts the hydrating cement at a timevery close to the commencing of mixing, as in the precast case. Someready-mix operations include one or more additional operations afterbatching but before the truck has left the batching facility, e.g., awash station for washing the truck after batching, and in theseoperations carbon dioxide may be alternatively or additionally added atthe batching facility after batching, e.g., at a wash station, whichwill involve carbon dioxide addition at a time several minutes aftermixing commences. Additionally or alternatively, carbon dioxide may beadded at the job site after the concrete has been transported, and inthese cases carbon dioxide addition will be added to mixing concrete ata time up to several hours after mixing commences. Any suitablecombination of these approaches may be used.

Thus, in certain embodiments, carbon dioxide is applied to the mix at 0minutes, that is, carbon dioxide is present to the mix chamber when thefirst mix water is supplied, or supplying carbon dioxide to the mixchamber commences when the first mix water is applied, or both. Incertain embodiments, carbon dioxide is applied at least 0, 1, 5, 10, 20,30, 40, or 50 seconds, or 1, 2, 5, 10, 15, 20, 30, 40, 50, 60, 70, 80,or 90 minutes after mixing commences, and/or not more than 1, 2, 5, 10,15, 20, 30, 40, 50, 60, 70, 80, 90, 120, 180, 240, or 300 minutes aftermixing commences. The duration of carbon dioxide delivery can be lessthan or equal to 10, 8, 7, 6, 5, 4, 3, 2, or 1 minute, or less than orequal to 50, 40, or 30 seconds, and/or more than or equal to 5, 10, 20,30, 40, or 50 seconds, or more than or equal to 1, 2, 3, 4, 5, 6, 7, or8 minutes. In certain embodiments, the duration of carbon dioxidedelivery is 5 seconds to 5 minutes. In certain embodiments, the durationof carbon dioxide delivery is 10 seconds to 4 minutes. In certainembodiments, the duration of carbon dioxide delivery is 20 seconds to 3minutes. In certain embodiments, carbon dioxide delivery commences notmore than 1 minute after mixing commences. For example, in the case ofcarbon dioxide supplied to a concrete mix in a ready mix truck, the mixcomponents, including at least part of the mix water, may be added tothe truck, and it may be desirable that carbon dioxide addition notcommence until at least 2, 3 or 4 minutes or more after mixing hascommenced. Such addition could occur, e.g., at a wash station, where thedriver stops to wash the truck before commencing delivery; the truck isusually stopped at the wash station for at least 5-10 minutes, and anon-site carbon dioxide delivery system can be used to supply carbondioxide to the drum of the truck during the wash station stop. Part orall of the dose of carbon dioxide can be delivered in this manner, forexample by delivering carbon dioxide to the truck through the water line(though any suitable route may be used); in embodiments where a carbondioxide source is attached to the truck there may be some mechanism toremind the driver to detach it before departing, such as an alarm.Alternatively, or additionally, the desirable time for addition ofcarbon dioxide to the mix may be later in the mix time, such as at atime that the truck is normally en route to the job site, or at the jobsite. In this case, a portable source of carbon dioxide may be attachedto the truck, with suitable valving and tubing, so as to deliver one ormore doses of carbon dioxide to the drum of the truck at a later time,such as at least 15, 30, or 60 minutes after mixing commences. Acontroller, which may be self-contained or may be remotely activated andwhich may send signals to a remote site regarding dosing and otherinformation, may be included in the system so that dosing commences at apredetermined time after mixing commences and continues for apredetermined time, or continues until some predetermined characteristicor characteristics of the concrete mix is detected. Alternatively, thetime and/or duration of dosing may be manually controlled, or subject tomanual override. The carbon dioxide source can be as simple as apressurized tank of gaseous carbon dioxide, which can be topped offperiodically, for example when the truck returns to the batching site,to ensure a sufficient supply of carbon dioxide for any ensuing round ofcarbonation, e.g., without the need to ascertain carbon dioxide levelsin the tank. In these embodiments, some or all of the carbonation mayoccur at the job site, for example, based on determination of one ormore characteristics of the concrete.

The rate of delivery of the carbon dioxide may be any desired rate andthe rate may be controlled. A slower rate of delivery may be desired,especially in wet mix operations such as ready mix operations, where thehigher w/c ratio is known to slow carbonation compared to lower w/coperations, e.g., some precast operations. One example for controllingthe rate of delivery is to divide the total dose of carbon dioxide intotwo or more smaller doses. Thus, the carbon dioxide may be delivered asa single dose, or as multiple doses, for example, as at least 2, 3, 4,5, 6, 7, 8, 9, or 10 doses, and/or not more than 3, 4, 5, 6, 7, 8, 9,10, 12, 15, or 20 doses; such as 2-10 doses, or 2-5 doses. Each dose maybe equal in size to the others or different, and the interval betweendoses may be timed equally or not, as desired. The exact number and sizeof the doses may be predetermined, or it may be dictated by one or morecharacteristics of the mix that are monitored. The carbon dioxide may bein any suitable form, such as gas, or a gas/solid mix.

In addition or alternatively, for slower rates of delivery where therate is controlled, gaseous carbon dioxide carbon dioxide may bedelivered at a controlled, relatively slow rate. Thus, in someembodiments, the carbon dioxide is delivered at least in part as a gasat a controlled rate, where the rate may be not more than 5, 10, 20, 30,40, 50, 60, 70, 80, 90, 100, 120, 150, 200, 300, 400, 500, 600, 700, or800 SLPM (standard liters per minute), and or not less than 10, 20, 30,40, 50, 60, 70, 80, 90, 100, 120, 150, 200, 300, 400, 500, 600, 700,800, or 900 SLPM. For example, in a ready mix truck en route to a jobsite, the carbon dioxide may be delivered at a rate such that the fulldose is delivered while the truck is in transit, e.g., by a portabledosing system as described above, over a period of many minutes or evenan hour or more, such as at a rate of 100 to 600 SLPM, or even lowerrates. The rate of delivery may be constant, or it may be variedaccording to a predetermined schedule, or as dictated by one or morecharacteristics of the concrete mix that are monitored. Either or bothof divided doses and controlled rate dosing may be used, as desired ordictated by the particular mix and job requirements.

The methods and compositions of the invention allow for very high levelsof efficiency of uptake of carbon dioxide into the mixing concrete,where the efficiency of uptake is the ratio of carbon dioxide thatremains in the mixing concrete as stable reaction products to the totalamount of carbon dioxide to which the mixing concrete is exposed. Incertain embodiments, the efficiency of carbon dioxide uptake is at least40, 50, 60, 70, 80, 90, 95, 96, 97, 98, 99, or 99%, or 40-100, 50-100,60-100, 70-100, 80-100, 90-100, 40-99, 50-99, 60-99, 70-99, 80-99, or90-99%.

In a wet cast operation, the addition of carbon dioxide, components ofthe cement mix, e.g., hydraulic cement mix, such as one or moreadmixtures, described more fully below, may be adjusted so thatflowability of the final cement mix, e.g., hydraulic cement mix iswithin 10% of the flowability that would be achieved without theaddition of carbon dioxide. In certain embodiments, the addition ofcarbon dioxide, components of the cement mix, e.g., hydraulic cementmix, such as one or more admixtures, described more fully below, areadjusted so that flowability of the final cement mix, e.g., hydrauliccement mix is within 50, 40, 30, 20 15, 10, 8, 5, 4, 3, 2, or 1% of theflowability that would be achieved without the addition of carbondioxide, or of a predetermined flowability. In certain embodiments, theaddition of carbon dioxide, components of the cement mix, e.g.,hydraulic cement mix, such as one or more admixtures, described morefully below, are adjusted so that flowability of the final cement mix,e.g., hydraulic cement mix is within 20% of the flowability that wouldbe achieved without the addition of carbon dioxide, or a predeterminedflowability. In certain embodiments, the addition of carbon dioxide,components of the cement mix, e.g., hydraulic cement mix, such as one ormore admixtures, described more fully below, are adjusted so thatflowability of the final cement mix, e.g., hydraulic cement mix iswithin 10% of the flowability that would be achieved without theaddition of carbon dioxide, or a predetermined flowability. In certainembodiments, the addition of carbon dioxide, components of the cementmix, e.g., hydraulic cement mix, such as one or more admixtures,described more fully below, are adjusted so that flowability of thefinal cement mix, e.g., hydraulic cement mix is within 5% of theflowability that would be achieved without the addition of carbondioxide, or a predetermined flowability. In certain embodiments, theaddition of carbon dioxide, components of the cement mix, e.g.,hydraulic cement mix, such as one or more admixtures, described morefully below, are adjusted so that flowability of the final cement mix,e.g., hydraulic cement mix is within 2% of the flowability that would beachieved without the addition of carbon dioxide, or a predeterminedflowability. In certain embodiments, the addition of carbon dioxide,components of the cement mix, e.g., hydraulic cement mix, such as one ormore admixtures, described more fully below, are adjusted so thatflowability of the final cement mix, e.g., hydraulic cement mix iswithin 1-50%, or 1-20%, or 1-10%, or 1-5%, or 2-50%, or 2-20%, or 2-10%,or 2-5% of the flowability that would be achieved without the additionof carbon dioxide, or a predetermined flowability.

A. Admixtures

Admixtures are often used in cement mix, e.g., hydraulic cement mixes,such as concrete mixes, to impart desired properties to the mix.Admixtures are compositions added to a cement mix, e.g., hydrauliccement mix such as concrete to provide it with desirable characteristicsthat are not obtainable with basic cement mix, e.g., hydraulic cementmixes, such as concrete mixtures or to modify properties of the cementmix, e.g., hydraulic cement mix, i.e., concrete to make it more readilyuseable or more suitable for a particular purpose or for cost reduction.An admixture is any material or composition, other than the hydrauliccement, aggregate and water, that is used as a component of the cementmix, e.g., hydraulic cement mix, such as concrete or mortar to enhancesome characteristic, or lower the cost, thereof. In some instances, thedesired cement mix, e.g., hydraulic cement mix, e.g., concreteperformance characteristics can only be achieved by the use of anadmixture. In some cases, using an admixture allows for the use of lessexpensive construction methods or designs, the savings from which canmore than offset the cost of the admixture.

In certain embodiments, the carbonated cement mix, e.g., hydrauliccement mixture, e.g., concrete, may exhibit enhanced characteristicswhen compared with the same mixture that was not exposed to carbondioxide. This can depend on the type of cement used in the carbonatedcement mix and/or the dose of carbon dioxide used and final carbonationachieved. In this sense, carbon dioxide can itself act as an admixture.For example, in certain embodiments, the carbonated cement mix, e.g.,concrete mixture, has superior properties such as greater strength, suchas greater 1-, 7-, or 28-day strength, e.g., at least 1, 2, 3, 4, 5, 7,10, 15, 20, 30, or 40% greater strength than the non-carbonated concretemixture at 1-, 7-, or 28-days. In general herein, “strength” refers tocompressive strength, as that term is generally understood in the art.In certain embodiments, the carbonated cement mix, e.g. concrete, mayexhibit accelerated set compared to non-carbonated mix, such as a fastertime to initial set (for example, penetrometer measurement of 500 psiaccording to ASTM C403) or a faster time to final set (for example,penetrometer measurement of 4000 psi according to ASTM C403), or both,such as less than 95, 90, 85, 80, 75, 70, 65, 60, 55, 50, 40, 30, or 20%of the initial or final set time compared to uncarbonated mix.Carbonated cement mix, e.g., hydraulic cement mixes may also providefinal concrete mixtures that have lower water absorption as compared tonon-carbonated, such as at least 1, 2, 3, 4, 5, 7, 10, 15, 20, 30, or40% lower water absorption. The carbonated cement mix, e.g., hydrauliccement mix, i.e., concrete, may also produce a final product that islower in density but of comparable strength compared to non-carbonated,such as at least 1, 2, 3, 4, 5, 7, 10, 15, 20, 30, or 40% lower densitywith a compressive strength within 1, 2, 3, 4, 5, 7, 10, 15, or 20% ofthe non-carbonated, e.g., at least 5% lower density with a compressivestrength within 2%.

However, depending on the mix design, the carbonated cement mix, e.g.,hydraulic cement mixture, i.e., concrete, may alternatively or inaddition, exhibit properties that it is desired to modulate, such as bythe addition of an admixture. For example, carbonated cement mix, e.g.,hydraulic cement mix for use in a wet cast operation may haveworkability/flow characteristics that are not optimum for a wet castoperation without addition of an admixture or other manipulation of themix, e.g., addition of extra water. As another example, carbonated mixesmay have strength characteristics, e.g., compressive strength at one ormore time points, that are not optimum without addition of an admixtureor other manipulation of the mix. In some cases, the mix design willalready call for an admixture, whose effect on the properties of the mixmay be affected by the carbonation, requiring coordination of the timingof the admixture in relation to the carbon dioxide addition, or othermanipulation. In addition, an admixture may be used to modulate one ormore aspects of the carbonation itself, for example, to increase therate of uptake of the carbon dioxide.

Concrete may be used in wet cast operations, such as in certain precastoperations or in ready mix trucks that transport the concrete to a jobsite where it is used, e.g., poured into molds or otherwise used at thesite, or in dry cast operations, which are precast operations. In thecase of a wet cast operation, the flowability of the concrete should bemaintained at a level compatible with its use in the operation, e.g., inthe case of a ready mix truck, at the job site; whereas for a dry castoperation concrete that does not flow (zero slump) is desirable. In bothdry cast and wet cast operations, strength, e.g., compressive strength,is important, both in the short term so that the concrete can be allowedto stand alone, e.g., molds can be removed, cast objects can bemanipulated, etc., in the shortest possible time, and also in the longterm so that a required final strength is reached. Flowability of a mixmay be evaluated by measuring slump; strength may be evaluated by one ormore strength tests, such as compressive strength. Other properties thatmay be affected by carbonation; in some cases the effect is a positiveone, but if the effect is a negative one, corrected through the use ofone or more admixtures. Such properties include shrinkage and waterabsorption.

In certain cases carbonation of the cement mix, e.g., hydraulic cementmix may affect flowability of a cement mix, e.g., hydraulic cement mix,i.e., a concrete mix, to be used in a wet cast operation, such as in aready mix truck transporting the mix to a job site. Thus in certainembodiments in which a carbonated mix is produced (such as for use witha readymix truck), one or more admixtures may be added to modulate theflowability of the carbonated mixture, either before, during, or aftercarbonation, or any combination thereof, such that it is within acertain percentage of the flowability of the same mixture withoutcarbonation, or of a certain predetermined flowability. The addition ofcarbon dioxide, components of the mix, e.g., concrete mix, and/oradditional components such as one or more admixtures, may be adjusted sothat flowability of the final mix is within 50, 40, 30, 20, 10, 8, 5, 4,3, 2, 1, 0.5, or 0.1% of the flowability that would be achieved withoutthe addition of carbon dioxide, or of a certain predeterminedflowability. In certain embodiments, the addition of carbon dioxide,components of the mix, and/or additional components such as one or moreadmixtures, may be adjusted so that flowability of the final mix iswithin 20% of the flowability that would be achieved without theaddition of carbon dioxide, or within 20% of a predetermined desiredflowability. In certain embodiments, the addition of carbon dioxide,components of the mix, and/or additional components such as one or moreadmixtures, may be adjusted so that flowability of the final mix iswithin 10% of the flowability that would be achieved without theaddition of carbon dioxide, or within 10% of a predetermined desiredflowability. In certain embodiments, the addition of carbon dioxide,components of the mix, and/or additional components such as one or moreadmixtures, may be adjusted so that flowability of the final mix iswithin 5% of the flowability that would be achieved without the additionof carbon dioxide, or within 5% of a predetermined desired flowability.In certain embodiments, the addition of carbon dioxide, components ofthe mix, and/or additional components such as one or more admixtures,may be adjusted so that flowability of the final mix is within 2% of theflowability that would be achieved without the addition of carbondioxide, or within 2% of a predetermined desired flowability. Anysuitable measurement method for determining flowability may be used,such as the well-known slump test. Any suitable admixture may be used,as described herein, such as carbohydrates or carbohydrate derivatives,e.g., fructose, sucrose, glucose, sodium glucoheptonate, or sodiumgluconate, such as sodium glucoheptonate or sodium gluconate.

In certain embodiments, one or more admixtures may be added to modulatethe mix so that a desired strength, either early strength, latestrength, or both, may be achieved. Strength of the carbonated cementmix can be dependent on mix design, thus, although with some mix designscarbonation may increase strength at one or more time points, in othermix designs carbonation may decrease strength at one or more timepoints. See Examples for various mix designs in which carbonationincreased or decreased strength at one or more time points. In somecases, carbonation decreases strength at one or more time points and itis desired to return the strength at the time point to within a certainacceptable limit. In certain cases, one or more admixtures is added toincrease strength beyond that seen in non-carbonated concrete of thesame density. This may be done, e.g., to produce a lightweight concretewith strength comparable to the denser, non-carbonated concrete. Inother cases, one or more admixtures added to a carbonated cement itselfcauses or exacerbates strength loss, and it is desired to recover theloss. Thus, in certain embodiments an admixture is added to thecarbonated mix, either before, during, or after carbonation, or acombination thereof, under conditions such that the carbonated mixexhibits strength, e.g., 1-, 7-, 28 and/or 56-day compressive strength,within a desired percentage of the strength of the same mix withoutcarbonation, or of a predetermined strength, e.g., within 50, 40, 30,20, 15, 12, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0.5, or 0.1%. In certainembodiments, the addition of carbon dioxide, components of the mix,and/or additional components such as one or more admixtures, may beadjusted so that strength at a given time point of the final mix iswithin 20% of the strength that would be achieved without the additionof carbon dioxide, or within 20% of a predetermined desired strength. Incertain embodiments, the addition of carbon dioxide, components of themix, and/or additional components such as one or more admixtures, may beadjusted so that strength at a given time point of the final mix iswithin 10% of the strength that would be achieved without the additionof carbon dioxide, or within 10% of a predetermined desired strength. Incertain embodiments, the addition of carbon dioxide, components of themix, and/or additional components such as one or more admixtures, may beadjusted so that strength at a given time point of the final mix iswithin 5% of the strength that would be achieved without the addition ofcarbon dioxide, or within 5% of a predetermined desired strength. Incertain embodiments, the addition of carbon dioxide, components of themix, and/or additional components such as one or more admixtures, may beadjusted so that strength at a given time point of the final mix iswithin 2% of the strength that would be achieved without the addition ofcarbon dioxide, or within 2% of a predetermined desired strength. Incertain embodiments the strength is a compressive strength. Any suitablemethod to test strength, such as flexural or compressive strength, maybe used so long as the same test is used for samples with and withoutcarbonation. Any suitable admixtures to achieve the desired strengthsmay be used, such as the admixtures described herein.

Other properties, such as water absorption, shrinkage, chloridepermeability, and the like, may also be tested and adjusted in a similarmanner, and to similar percentages, as for flowability and/or shrinkage.

It will be appreciated that more than one admixture may be used, forexample, 2, 3, 4, 5, or more than 5 admixtures. For example, certainadmixtures have desirable effects on flowability but undesirable effectson strength development; when such an admixture is used, a secondadmixture that accelerates strength development may also be used.

Any suitable admixture that has the desired effect on the property orproperties of the carbonated cement that it is desired to modified maybe used. TABLE 1 lists exemplary classes and examples of admixtures thatcan be used, e.g., to modulate the effects of carbonation.

TABLE 1 Admixtures for use with carbonated cement Cement Chemical ClassSub Class Application Examples Saccharides Sugars Retarder Fructose,glucose, sucrose Sugar Acids/bases Retarder Sodium Gluconate, sodiumglucoheptonate Organic Polymers Polycarboxylic Plasticizer Manycommercial brands Ethers Sulfonated Plasticizer Many commercial brandsNapthalene Formaldehyde Sulphonated Plasticizer Many commercial brandsMelamine formaldehyde Ligno sulphonates Plasticizer Many commercialbrands Inorganic Salts Alkaline Earth Accelerant Ca(NO₃)₂, Mg(OH)₂ MetalContaining Alkali Metal Accelerant NaCl, KOH Containing Carbonate —NaHCO₃, Na₂CO₃ containing Alkanolamines Tertiary Accelerants/GrindingTriethanolamine, alkanolamines aids Triisopropylamine Phosphonates —Retarders Nitrilotri(methylphosphonic acid), 2-phosphonobutane-1,2,4-tricarboxylic acid Surfactants Vinsol Resins, Air Entraining Manycommercial brands synthetic Agents surfactants Chelating Agents VariousRetarders EDTA, Citric Acid, Chemistries nitrilotriacetic acid

In certain embodiments, one or admixtures is added to a cement mix,e.g., hydraulic cement mix, before, during, or after carbonation of themix, or a combination thereof, where the admixture is a set retarder,plasticizer, accelerant, or air entraining agent. Where it is desired tomodulate flowability, set retarders and plasticizers are useful. Whereit is desired to modulate strength development, accelerants are useful.If it is desired to increase the rate of carbon dioxide uptake, certainair entraining agents may be useful.

Set retarders include carbohydrates, i.e., saccharides, such as sugars,e.g., fructose, glucose, and sucrose, and sugar acids/bases and theirsalts, such as sodium gluconate and sodium glucoheptonate; phosphonates,such as nitrilotri(methylphosphonic acid),2-phosphonobutane-1,2,4-tricarboxylic acid; and chelating agents, suchas EDTA, Citric Acid, and nitrilotriacetic acid. Other saccharides andsaccharide-containing admixes include molasses and corn syrup. Incertain embodiments, the admixture is sodium gluconate. Other exemplaryadmixtures that can be of use as set retarders include sodium sulfate,citric acid, BASF Pozzolith XR, firmed silica, colloidal silica,hydroxyethyl cellulose, hydroxypropyl cellulose, fly ash (as defined inASTM C618), mineral oils (such as light naphthenic), hectorite clay,polyoxyalkylenes, natural gums, or mixtures thereof, polycarboxylatesuperplasticizers, naphthalene HRWR (high range water reducer).Additional set retarders that can be used include, but are not limitedto an oxy-boron compound, lignin, a polyphosphonic acid, a carboxylicacid, a hydroxycarboxylic acid, polycarboxylic acid, hydroxylatedcarboxylic acid, such as fumaric, itaconic, malonic, borax, gluconic,and tartaric acid, lignosulfonates, ascorbic acid, isoascorbic acid,sulphonic acid-acrylic acid copolymer, and their corresponding salts,polyhydroxysilane, polyacrylamide. Illustrative examples of retardersare set forth in U.S. Pat. Nos. 5,427,617 and 5,203,919, incorporatedherein by reference.

Accelerants include calcium-containing compounds, such as CaO, Ca(NO₂)₂,Ca(OH)₂, calcium stearate, or CaCl₂, and magnesium-containing compounds,such as magnesium hydroxide, magnesium oxide, magnesium chloride, ormagnesium nitrate. Without being bound by theory, it is thought that, inthe case of carbonated cement, the added calcium or magnesium compoundmay provide free calcium or magnesium to react with the carbon dioxide,providing a sink for the carbon dioxide that spares the calcium in thecement mix, or providing a different site of carbonation than that ofthe cement calcium, or both, thus preserving early strength development.In certain embodiments, CaO (lime) may be added to the mix, or ahigh-free lime cement may be the preferred cement for the mix. Forexample, in certain embodiments, the free lime (CaO) content of thecement used in a particular cement mixture, such as mortar or concrete,may be increased by the addition of CaO to the mixture, generally beforethe mixture is exposed to carbon dioxide, such as by addition of0.01-50%, or 0.01-10%, or 0.01-5%, or 0.01-3%, or 0.01-2%, or 0.01-1%CaO, or 0.1-50%, or 0.1-10%, or 0.1-5%, or 0.1-3%, or 0.1-2%, or 0.1-1%,or 0.2-50%, or 0.2-10%, or 0.2-5%, or 0.2-3%, or 0.2-2% CaO, or 0.2-1%,or 0.5-50%, or 0.5-10%, or 0.5-5%, or 0.5-3%, or 0.5-2% CaO, or 0.5-1%CaO bwc. Alternatively, CaO may be added so that the overall CaO contentof the cement mixture reaches a desired level, such as 0.5-10%, or0.5-5%, or 0.5-3%, or 0.5-2%, or 0.5-1.5%, or at least 0.5, 0.6, 0.7,0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.2,2.5, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, 10%, 20%, 30%, 40%, or 50% CaObwc. The added CaO will generally also increase the rate of uptake ofcarbon dioxide by the mix during mixing, thus allowing a greater carbondioxide uptake for a given time of exposure, or a lower time of exposureto achieve a given level of uptake. Other set accelerators include, butare not limited to, a nitrate salt of an alkali metal, alkaline earthmetal, or aluminum; a nitrite salt of an alkali metal, alkaline earthmetal, or aluminum; a thiocyanate of an alkali metal, alkaline earthmetal or aluminum; an alkanolamine; a thiosulfate of an alkali metal,alkaline earth metal, or aluminum; a hydroxide of an alkali metal,alkaline earth metal, or aluminum; a carboxylic acid salt of an alkalimetal, alkaline earth metal, or aluminum (preferably calcium formate); apolyhydroxylalkylamine; a halide salt of an alkali metal or alkalineearth metal (e.g., chloride).

The admixture or admixtures may be added to any suitable finalpercentage (bwc), such as in the range of 0.01-0.5%, or 0.01-0.3%, or0.01-0.2%, or 0.01-0.1%, or 0.01-1.0%, or 0.01-0.05%, or 0.05% to 5%, or0.05% to 1%, or 0.05% to 0.5%, or 0.1% to 1%, or 0.1% to 0.8%, or 0.1%to 0.7% per weight of cement. The admixture may be added to a finalpercentage of greater than 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07,0.08, 0.09, 0.1, 0.15, 0.2, 0.3, 0.4, or 0.5%; in certain cases alsoless than 5, 4, 3, 2, 1, 0.9, 0.8, 0.7, 0.6, 0.5, 0.4, 0.3, 0.2, 0.1,0.09, 0.08, 0.07, 0.06, 0.05, 0.04, 0.03, or 0.02%.

It has been observed that the timing of addition of a given admixturerelative to carbonation of a cement mix, e.g., hydraulic cement mix mayalter the effects of the admixture on the properties of the cement mix,e.g., hydraulic cement mix, e.g., effects on flowability or strength.For example, in certain mix designs, the addition of sodium gluconateafter carbonation restores flowability to desired levels, but mayadversely affect early strength development; whereas the addition ofsodium gluconate before carbonation maintains early strength developmentbut does not optimally restore flowability. As another example, in mixdesigns in which an air entrainer is desired, it has been found that ifthe air entrainer is added before carbonation, the density of the mix isincreased compared to if the air entrainer is added after carbonation.The admixture or admixtures thus may be added before, during, or aftercarbonation of the cement mix, e.g., hydraulic cement mix, or anycombination thereof. For example, in certain embodiments, the admixtureis added after carbonation; in other embodiments, the admixture is addedbefore carbonation; in yet other embodiments, the admixture is added intwo split doses, one before carbonation and one during and/or aftercarbonation. It will be apparent that if more than one admixture isused, one may be added at one time while another is added at anothertime, for example, in a mix where an air entrainer is used and sodiumgluconate is also added to affect flowability, the sodium gluconate maybe added in split doses, one before carbonation and one during/aftercarbonation, and the air entrainer may be added after carbonation. Thelatter is exemplary only, and any suitable combination of admixtures andtiming to achieve the desired effect or effects may be used.

It has been observed that the effects of carbonation and of admixtureson carbonated cement mix, e.g., hydraulic cement mixes is highlymix-specific. In some cases carbonation actually improves the propertiesof a mix, especially in dry cast situations where flowability is not anissue, and no admixture is required. In other cases, especially in wetcast situations where flowability is an issue, one or more admixturesmay be required to restore one or more properties of the mix. Whether ornot admixture is added, and/or how much is added, to a given batch maybe determined by pre-testing the mix to determine the properties of thecarbonated mix and the effects of a given admixture. In some cases theadmixture and/or amount may be predicted based on previous tests, or onproperties of the cement used in the mix, or on theoreticalconsiderations. It has been found that different cements have differentproperties upon carbonation, and also react differently to a givenadmixture, and the invention includes the use of a library of data onvarious cement types and admixtures so as to predict a desiredadmixture/amount for a mix design, which may be a mix that is the sameas or similar to a mix in the library, or a new mix whose properties canbe predicted from the library. In addition, for a given batch, rheology(flowability) may be monitored during the carbonation of the batch andthe exact timing and/or amount of admixture added to that particularbatch, or to subsequent batches, may be adjusted based on the feedbackobtained. A combination of predicted value for admixture type, timing,and/or amount, and modification of the value based on real-timemeasurements in a given batch or batches may be used.

In certain embodiments, an admixture comprising a carbohydrate orcarbohydrate derivative is added to a cement mix, e.g., hydraulic cementmix before, during, and/or after carbonation of the mix, or acombination thereof. In certain embodiments, the admixture is addedafter carbonation of the cement mix, e.g., hydraulic cement mix, orduring and after carbonation. The carbonation may be accomplished asdescribed herein, for example, by delivering carbon dioxide to thesurface of the cement mix, e.g., hydraulic cement mix during mixing. Thecarbohydrate or derivative may be any carbohydrate as described herein,for example sucrose, fructose, sodium glucoheptonate, or sodiumgluconate. In certain embodiments, the carbohydrate is sodium gluconate.The carbohydrate or derivative, e.g., sodium gluconate may be used at asuitable concentration; in some cases, the concentration is greater than0.01%, 0.015%, 0.02%, 0.025%, 0.03%, 0.035%, 0.04%, 0.05%, 0.06%, 0.07%,0.08%, 0.09%, 0.1%, 0.15%, 0.2%, 0.3%, 0.4%, or 0.5% bwc. Theconcentration may also be less than 2, 1.5, 1, 0.9, 0.8, 0.7, 0.6, 0.5,0.4, 0.3, 0.2, or 0.1%. For example, in certain embodiments, sodiumgluconate is used as an admixture at a dose of between 0.01 and 1% bwc,or between 0.01 and 0.8%, or between 0.01 and 0.5%, or between 0.01 and0.4% bwc, or between 0.01 and 0.3%, or between 0.01 and 0.2% bwc, orbetween 0.01 and 0.1%, or between 0.01 and 0.05%, or between 0.03 and 1%bwc, or between 0.03 and 0.8%, or between 0.03 and 0.5%, or between 0.03and 0.4% bwc, or between 0.03 and 0.3%, or between 0.03 and 0.2% bwc, orbetween 0.03 and 0.1%, or between 0.03 and 0.08%, or between 0.05 and 1%bwc, or between 0.05 and 0.8%, or between 0.05 and 0.5%, or between 0.05and 0.4% bwc, or between 0.05 and 0.3%, or between 0.05 and 0.2% bwc, orbetween 0.05 and 0.1%, or between 0.05 and 0.08%, or between 0.1 and 1%bwc, or between 0.1 and 0.8%, or between 0.1 and 0.5%, or between 0.1and 0.4% bwc, or between 0.1 and 0.3%, or between 0.1 and 0.2% bwc. Thesodium gluconate may be added before, during, or after carbonation ofthe mix, or any combination thereof, and may be added as one, two,three, four, or more than four divided doses. The carbohydrate orderivative may be added in two or more doses, such as one dose beforecarbonation and one dose during and/or after carbonation. In certainembodiments, calcium stearate is used as an admixture.

In certain embodiments, a second admixture is also used, such as any ofthe admixtures described herein. In certain embodiments, the secondadmixture is a strength accelerator. In certain embodiments, a thirdadmixture is also used, such as any of the admixtures described herein.In certain embodiments, a fourth admixture is also used, such as any ofthe admixtures described herein.

In certain embodiments, an admixture is used that modulates theformation of calcium carbonate so that one or more polymorphic forms isfavored compared to the mixture without the admixture, e.g., modulatesthe formation of amorphous calcium carbonate, e.g., aragonite, orcalcite. Exemplary admixtures of this type include organic polymers suchas polyacrylate and polycarboxylate ether, phosphate esters such ashydroxyamino phosphate ester, phosphonate and phosphonic acids such asnitrilotri(methylphosphonic acid), 2-phosphonobutane-1,2,4-tricarboxylicacid, chelators, such as sodium gluconate, ethylenediaminetetraaceticacid (EDTA), and citric acid, or surfactants, such as calcium stearate.

Other admixtures useful in methods and compositions of the invention aredescribed in U.S. Pat. No. 7,735,274, hereby incorporated by referenceherein in its entirety.

B. Supplementary Cementitious Materials and Cement Replacements

In certain embodiments, one or more supplementary cementitious materials(SCMs) and/or cement replacements are added to the mix at theappropriate stage for the particular SCM or cement replacement. Incertain embodiments, an SCM is used. Any suitable SCM or cementreplacement may be used; exemplary SCMs include blast furnace slag, flyash, silica fume, natural pozzolans (such as metakaolin, calcined shale,calcined clay, volcanic glass, zeolitic trass or tuffs, rice husk ash,diatomaceous earth, and calcined shale), and waste glass. Further cementreplacements include interground limestone, recycled/waste plastic,scrap tires, municipal solid waste ash, wood ash, cement kiln dust,foundry sand, and the like. In certain embodiments, an SCM and/or cementreplacement is added to the mix in an amount to provide 0.1-50%, or1-50%, or 5-50%, or 10-50%, or 20-50%, or 1-40%, or 5-40%, or 10-50%, or20-40% bwc. In certain embodiments, an SCM is used and the SCM is flyash, slag, silica fume, or a natural pozzolan. In certain embodiment,the SCM is fly ash. In certain embodiments, the SCM is slag.

It is well-known that addition of an SCM such as fly ash or slag to acement mix, e.g., concrete mix, can retard early strength development;indeed, when weather becomes cold enough, the use of SCM in mixes iscurtailed because the early strength development is sufficientlyretarded as to make the use of the mix problematic. In addition, themaximum amount of SCM that may be added to a mix can be limited by itseffect on early strength development. The present inventors have foundthat even very low doses of carbon dioxide, when added to a concrete mixcontaining SCM, can accelerate early strength development and thus couldallow such mixes to be used under circumstances where they otherwisemight not be used, e.g., in cold weather, or in greater amounts, thusextending the usefulness of such mixes, such as extending the usefulseason for such mixes, or increasing the proportion of SCM in a givenmix, or both.

In certain embodiments the invention provides methods and compositionsfor the expanding the range of conditions under which an SCM may be usedin a concrete mix by carbonating the mix. The range of conditions mayinclude the temperature at which the SCM-containing mix may be used, orthe amount of SCM that may be added while maintaining adequate earlystrength development, or the early strength for a given amount of SCM ina mix.

In certain embodiments, the invention provides a method for decreasingthe minimum temperature at which an SCM-concrete mix may be used, thusincreasing the overall acceptable temperature range for the SCM-concretemix, by exposing the SCM-concrete mix to a dose of carbon dioxidesufficient to modulate, e.g., accelerate, early strength developmentand/or set of the mix to a level at which the mix may be used at atemperature below that at which it could have been used without thecarbon dioxide exposure. The dose can be such that the early strengthdevelopment of the mix allows its use in a desired manner at atemperature that is at least 1, 2, 3, 4, 5, 6, 8, 9, or 10° C. below thetemperature at which it could be used without the carbon dioxidetreatment and/or not more than 2, 3, 4, 5, 6, 8, 9, 10, or 12° C. belowthe temperature at which it could be used without the carbon dioxidetreatment. The dose of carbon dioxide added to the mix to achieve thedesired increase in early strength development can be not more than 2.0,1.5, 1.2, 1.0, 0.9, 0.8, 0.7, 0.6, 0.5, 0.4, 0.3, 0.2, 0.1, or 0.05%carbon dioxide bwc. The dose can be such that the early strengthdevelopment of the mix, e.g., the strength at 8, 12, 16, 20, or 24hours, or any other suitable time point for early strength development,is, on average, at least 1, 2, 5, 7, 10, 12, 15, 20, or 25% greater thanthe strength without the carbon dioxide dose, and is sufficient for theuse for which the mix is intended. In certain embodiments, analternative or additional marker other than early strength development,such as a value from calorimetry as described elsewhere herein, may beused instead of or in addition to early strength measurements, forexample, to determine the desired or optimal dose of carbon dioxideand/or dosing conditions. The carbon dioxide may be delivered as asingle dose or multiple doses, and at any suitable rate or in anysuitable form, as described elsewhere herein. The SCM can be anysuitable SCM. In certain embodiments, the SCM is fly ash. In certainembodiments, the SCM is slag. In certain embodiments, the SCM-concretemix is delivered to a job site in a ready mix truck, and the carbondioxide is applied to the mix at the batching site, en route to the jobsite, or at the job site, or any combination thereof. In certainembodiments, the carbon dioxide is gaseous carbon dioxide. In certainembodiments, the carbon dioxide is dissolved in mix water. In certainembodiments, the carbon dioxide is solid carbon dioxide. In certainembodiments, a combination of gaseous carbon dioxide and carbon dioxidedissolved in mix water is used.

In certain embodiments, the invention provides a method for increasingthe maximum amount (proportion) of SCM that may be used in anSCM-concrete mix, thus increasing the overall acceptable range ofamounts (proportions) of SCM for the SCM-concrete mix, by exposing anSCM-concrete mix that contains a proportion of SCM that would normallybe higher than the acceptable proportion due to effects on earlystrength development, to a dose of carbon dioxide sufficient tomodulate, e.g., accelerate, early strength development of the mix to alevel at which the mix may be used for its normal purposes. In certainembodiments, the maximum acceptable proportion of SCM in the mix isincreased by carbonation by at least 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 5,6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20% bwc and/ornot more than 1, 1.5, 2, 2.5, 3, 3.5, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13,14, 15, 16, 17, 18, 19, 20, or 25% bwc, over the maximum acceptableproportion of SCM without carbonation. The dose of carbon dioxide to themix can be not more than 2.0, 1.5, 1.2, 1.0, 0.9, 0.8, 0.7, 0.6, 0.5,0.4, 0.3, 0.2, 0.1, or 0.05% carbon dioxide bwc, and/or not less than2.5, 2.0, 1.5, 1.2, 1.0, 0.9, 0.8, 0.7, 0.6, 0.5, 0.4, 0.3, 0.2, or 0.1%carbon dioxide bwc. The SCM can comprises at least 1, 2, 3, 4, 5, 6, 7,8, 9, 10, 12, 15, 20, or 30% of the mix, and/or not less than 2, 3, 4,5, 6, 7, 8, 9, 10, 12, 15, 20, 30, 40, or 50% of the mix. The dose canbe such that the early strength development of the mix, e.g., thestrength at 8, 12, 16, 20, or 24 hours, or any other suitable time pointfor early strength development, is, on average, at least 1, 2, 5, 7, 10,12, 15, 20, or 25% greater than the strength without the carbon dioxidedose. In certain embodiments, an alternative or additional marker otherthan early strength development, such as a value from calorimetry asdescribed elsewhere herein, may be used instead of or in addition toearly strength measurements, for example, to determine the desired oroptimal dose of carbon dioxide and/or dosing conditions. The carbondioxide may be delivered as a single dose or multiple doses, and at anysuitable rate or in any suitable form, as described elsewhere herein.The SCM can be any suitable SCM. In certain embodiments, the SCM is flyash. In certain embodiments, the SCM is slag. In certain embodiments,the SCM-concrete mix is delivered to a job site in a ready mix truck,and the carbon dioxide is applied to the mix at the batching site, enroute to the job site, or at the job site, or any combination thereof.In certain embodiments, the carbon dioxide is gaseous carbon dioxide. Incertain embodiments, the carbon dioxide is dissolved in mix water. Incertain embodiments, the carbon dioxide is solid carbon dioxide. Incertain embodiments, a combination of gaseous carbon dioxide and carbondioxide dissolved in mix water is used.

In certain embodiments, the invention provides a method for acceleratingthe early strength development of an SCM-concrete mix, thus acceleratingaspects of a job in which the SCM-concrete mix is used that require acertain strength before a next step may be taken (such as removingmolds, adding a level of concrete, and the like), by exposing theSCM-concrete mix to a dose of carbon dioxide sufficient to modulate,e.g., accelerate, early strength development of the mix to a level atwhich the aspect of the job may be accelerated. The dose of carbondioxide to the mix can be not more than 2.0, 1.5, 1.2, 1.0, 0.9, 0.8,0.7, 0.6, 0.5, 0.4, 0.3, 0.2, 0.1, or 0.05% carbon dioxide bwc, and/ornot less than 2.5, 2.0, 1.5, 1.2, 1.0, 0.9, 0.8, 0.7, 0.6, 0.5, 0.4,0.3, 0.2, or 0.1% carbon dioxide bwc. The dose can be such that theearly strength development of the mix, e.g., the strength at 8, 12, 16,20, or 24 hours, or any other suitable time point for early strengthdevelopment, is, on average, at least 1, 2, 5, 7, 10, 12, 15, 20, 25,30, 35, or 40% greater than the strength without the carbon dioxidedose. The SCM can comprises at least 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12,15, 20, or 30% of the mix, and/or not less than 2, 3, 4, 5, 6, 7, 8, 9,10, 12, 15, 20, 30, 40, or 50% of the mix. In certain embodiments, analternative or additional marker than early strength development, suchas a value from calorimetry as described elsewhere herein, may be usedinstead of or in addition to early strength measurements, for example,to determine the desired or optimal dose of carbon dioxide and/or dosingconditions. The carbon dioxide may be delivered as a single dose ormultiple doses, and at any suitable rate or in any suitable form, asdescribed elsewhere herein. The SCM can be any suitable SCM. In certainembodiments, the SCM is fly ash. In certain embodiments, the SCM isslag. In certain embodiments, the SCM-concrete mix is delivered to a jobsite in a ready mix truck, and the carbon dioxide is applied to the mixat the batching site, en route to the job site, or at the job site, orany combination thereof. In certain embodiments, the carbon dioxide isgaseous carbon dioxide. In certain embodiments, the carbon dioxide isdissolved in mix water. In certain embodiments, the carbon dioxide issolid carbon dioxide. In certain embodiments, a combination of gaseouscarbon dioxide and carbon dioxide dissolved in mix water is used.

C. Control Mechanisms

The methods and apparatus described herein may include one or morecontrol mechanisms, e.g., automatic control mechanisms, to modulate oneor more aspects of the mix and carbonation operation, such as tomodulate the contact of the cement mix, e.g., hydraulic cement mix withcarbon dioxide and/or other components, such as one or more admixturesor water, as well as other aspects of the operation of the mixer, suchas worker safety requirements, cooling of the cement mix, e.g.,hydraulic cement mix, and the like. It will be appreciated thatmodulation may be achieved by human operators who control the necessaryvalves and the like to achieve a desired carbon dioxide exposure and/orother characteristic of the carbonated cement mix, but in generalautomatic control mechanisms are employed. The control may be based onany suitable parameter, such as feedback regarding one or morecharacteristics of the mix operation, timing, which may be apredetermined timing, or a combination thereof.

Control systems and mechanisms can apply to a stationary mixer in aprecast concrete plant or other central mixing facility. Alternatively,it can apply to a ready mix concrete truck that facilitates mixingthrough rotation of its drum. The mix operation can be a dry cast or wetcast operation; for example, the ready mix concrete truck will be a wetcast, while precast may be wet cast or dry cast.

A simple form of control is based on timing alone. Thus, in certainembodiments, the methods include modulating the flow of carbon dioxideto the cement mix, e.g., hydraulic cement mix according to a certaintiming. The timing may be controlled by a controller that is connectedto a cement mix, e.g., hydraulic cement mix apparatus and that senseswhen the apparatus has begun or stopped a stage of operation, and thatmodulates carbon dioxide flow accordingly, e.g., starts or stops flow.Thus in certain embodiments, carbon dioxide flow is begun when one ormore components of a cement mix, e.g., hydraulic cement mix have beendeposited in a mixer, continues for a certain predetermined time at acertain predetermined flow rate, then stops. The stage of operation ofthe cement mix, e.g., hydraulic cement mix apparatus may be determinedby the programming of the controller or of another controller to whichthe controller is operably connected, or it may be determined by one ormore sensors which monitor positions of components of the apparatus,flow, and the like, or a combination thereof.

Typically, however, control systems and mechanisms of the inventioninclude feedback mechanisms where one or more characteristics of thecement mix, e.g., hydraulic cement mixture and/or apparatus or itsenvironment is monitored by one or more sensors, which transmit theinformation to a controller which determines whether one or moreparameters of the mix operation requires modulation and, if so, sendsthe appropriate output to one or more actuators to carry out therequired modulation. The controller may learn from the conditions of onebatch to adjust programming for subsequent batches of similar or thesame mix characteristics to optimize efficiency and desiredcharacteristics of the mix.

In order to achieve a desired efficiency of carbon dioxide uptake in thecement mix, e.g., hydraulic cement mix, to ensure desiredcharacteristics such as flow characteristics, strength, and appearance,and/or to ensure worker safety, various aspects of the mix operation,the mixer, the cement mix, e.g., hydraulic cement mix, and theenvironment of the mixer may be monitored, the information from themonitoring processed, and adjustments made in one or more aspects of themix operation in order to achieve the desired result. Thus, in certainembodiments, one or more sensors may be used to provide input to acontroller as to various conditions related to the desiredcharacteristics; the controller processes the inputs and compares themto predetermined parameters of operation and, if corrections in theprocess are necessary, the controller then sends output to one or moreactuators in order to bring the system back toward the desiredcondition.

In particular embodiments, the invention provides control systems forcontrolling the carbonation of a cement mix, e.g., hydraulic cement mixin a mixer by use of one or more sensors monitoring one or more ofweight of the cement used in the mix, carbon dioxide concentration ofthe atmosphere inside and/or outside the mixer, temperature of thecement mix, e.g., hydraulic cement mix or a component in contact withthe cement mix, e.g., hydraulic cement mix, rheology of the mix, and/ormoisture content of the mix, where the one or more sensors send input toa controller which processes the information received from the one ormore sensors by comparing the input to one or more predeterminedparameters and, if necessary, sends output to one or more actuators toadjust carbon dioxide flow rate, water addition, or admixture addition,or to perform other functions such as to sound an alarm if carbondioxide levels exceed safe levels. In addition, certain operations, suchas cooling of the cement mix, e.g., hydraulic cement mix, may beperformed after the mixing is complete. The controller can learn fromone batch to adjust conditions for a subsequent batch of the same orsimilar composition. Further levels of control may be used, such as acentral controller that receives information from a plurality of mixoperations in a plurality of locations regarding one or more aspects ofeach operation, and processes the information received from all mixoperations to improve performance at the various operations; thus, largeamounts of information can be used to improve performance at a varietyof sites.

In the mixing operation, components of the cement mix, e.g., hydrauliccement mix, e.g., cement, aggregate, and water, are added to the mixer,and mixing commences. In some cases some components, such as aggregate,may have a sufficient water content, e.g., from exposure to wet weatherconditions, that additional water is not added before mixing commences.In some cases, as described elsewhere herein, water or other componentsmay be added in a staged manner. At some point before, during, or afterthe process of addition of components or mixing, carbon dioxide flow isinitiated from a source of carbon dioxide to the mixer. In some cases,part or all of the carbon dioxide will be included in the mix water. Insome cases, the carbon dioxide flow will be gaseous; in other cases, thecarbon dioxide flow comprises a mixture of gaseous and solid carbondioxide. Additional components, such as admixtures, may be added to thecement mix, e.g., hydraulic cement mix as well at any point in theoperation. The carbon dioxide is subsumed into the mixing cement mix,e.g., hydraulic cement mix and begins reaction with the mix components;any carbon dioxide that is not taken up by the cement mix, e.g.,hydraulic cement mix fills the head space of the mix container. Sincetypical mixers are not airtight, if the rate of carbon dioxide flow tothe mixer exceeds the rate of uptake into the cement mix, e.g.,hydraulic cement mix, at some point the head space in the mixer will befull of carbon dioxide and excess carbon dioxide will exit the mixerfrom one or more leak points. Thus, the carbon dioxide content of theatmosphere inside the mixer or, more preferably, outside the mixer,e.g., at one or more leak points, may be monitored to provide anindication that the rate of carbon dioxide addition is exceeding therate of carbon dioxide uptake. In addition, carbon dioxide levels inareas where workers are likely to be may also be monitored as a safetyprecaution. The reaction of carbon dioxide with the hydraulic cement isexothermic, thus the temperature of the cement mix, e.g., hydrauliccement mix rises; the rate of temperature rise is proportional to therate of carbon dioxide uptake and the overall temperature rise isproportional to total carbon dioxide uptake for a given mix design.Thus, the temperature of the cement mix, e.g., hydraulic cement mix, orthe temperature of one or more portions of the mix container or otherequipment that are in contact with the mix, may be monitored as anindication of rate and extent of carbon dioxide uptake into the cementmix, e.g., hydraulic cement mix. Carbonation of components of the cementmix, e.g., hydraulic cement mix may produce a change in the flowcharacteristics, i.e., rheology, of the cement mix, e.g., hydrauliccement mix, which can be undesirable in certain applications, e.g., inwet cast applications such as in a ready mix truck. Thus, the rheologyof the cement mix, e.g., hydraulic cement mix may be monitored. Inaddition, carbonation may affect the moisture characteristics of thecement mix, e.g., hydraulic cement mix, which may lead to undesirablecharacteristics, and moisture content of the mix may be monitored aswell.

The invention also provides a network of mix systems with one or moresensors and, optionally, controllers, that includes a plurality of mixsystems, such as 2, 3, 4, 5, 6, 7, 8, 9, 10, or more than 10 mix systemswith one or more sensors and, optionally, controllers, each of whichtransmits data from their respective locations and mix conditions to acentral controller, which learns from the overall data from all the mixsystems and provides updated and modified mix instructions to thevarious mix systems in the network based on this information. In thisway the operation of each individual mix system within the network canbe optimized based on information from all the other mix systems in thenetwork. Thus, timing and extent of carbon dioxide delivery, admixturetype and amount, water amount and timing and delivery, and other factorsmay be optimized for one site before it has even begun its first batch,based on historical information from other sites, and all sites mayundergo continual improvement in optimization as the sensors, and,optionally, controllers in the network continually gain more informationand feed it to the central controller.

Thus, in certain embodiments the methods and/or apparatus may includefeedback mechanisms by which one or more characteristics of the type ofmixer apparatus, cement mix, e.g., hydraulic cement mix, a gas mixturein contact with the cement mix, e.g., hydraulic cement mix and inside oroutside of the mixer, a component of the cement mix, e.g., hydrauliccement mix production apparatus, a component exposed to the cement mix,e.g., hydraulic cement mix, or the environment of the mixer, ismonitored and the information is used to modulate the exposure of thecement mix, e.g., hydraulic cement mix to carbon dioxide, one or moreadmixtures, water, or other components, in the current mix and/or insubsequent mixes. Characteristics such as carbon dioxide contentmonitored inside and/or outside the mixer, and/or temperature of the mixmonitored inside the mixer or outside of the mixer, of a component incontact with the cement mix, e.g., hydraulic cement mix, e.g., a surfaceof the mixer such as the outer surface of the mixer, and/or position orstate of operation of a component of the cement mix, e.g., hydrauliccement mix production apparatus, may be used to determine when tomodulate carbon dioxide addition, e.g., to start or to stop or slowcarbon dioxide addition. Certain safety monitoring may also be done,e.g., monitoring of areas outside the mixer for carbon dioxide levels toensure worker safety.

In general, feedback systems include one or more sensors for monitoringone or more characteristics and sending input to a controller, whichreceives the input from the sensors, processes it, and, if necessary,sends output, based on the processing, to one or more actuators that isconfigured to alter some aspect of the exposure of the cement mix, e.g.,hydraulic cement mix to carbon dioxide, water, admixture, or some otheraspect of the operation of the cement mix, e.g., hydraulic cement mixapparatus. In the simplest case, a human operator may manually begincarbon dioxide exposure by adjusting a valve, then may monitor acharacteristic by using one or more sensors, e.g., a handheldtemperature sensor that is pointed at the drum of a readymix truck,and/or a simple timer, and halt the supply of carbon dioxide gas when acertain temperature or a certain time is reached. However, in generalautomatic feedback mechanisms are used.

Sensors

Suitable sensors for use in control systems include temperature sensors,carbon dioxide sensors, rheology sensors, weight sensors (e.g., formonitoring the exact weight of cement used in a particular batch),moisture sensors, other gas sensors such as oxygen sensors, pH sensors,and other sensors for monitoring one or more characteristics of a gasmixture in contact with the cement mix, e.g., hydraulic cement mix, acomponent of the cement mix, e.g., hydraulic cement mix productionapparatus, a component exposed to the cement mix, e.g., hydraulic cementmix, or some other aspect of the mix operation. Sensors also includesensors that monitor a component of the cement mix, e.g., hydrauliccement mix apparatus, such as sensors that detect when mixing has begun,when components of a cement mix, e.g., hydraulic cement mix have beenadded to a mixer, mass flow sensors, flow rate or pressure meter in theconduit, or other suitable sensors.

Cement Weight Scale Sensor

A cement weight scale sensor can be used to transmit information to thecontroller concerning the mass of cement that will be in a given mixturein the mixer. Since the CO₂ is dosed in proportion to the mass ofcement, this weight is important for determining the correct dose toachieve the desired outcomes. The cement mass is also used to scale thesize of a given batch, given that a mixture could vary in relation to adefault size such as a full batch (100%) or a quarter batch (25%), orany other batch size. In some cases the batch could even exceed 100%.This batch size can also be used to determine the head (free) space inthe mixer so that it can be rapidly filled with CO₂ without creating anoverpressure by delivering more than the headspace will allow. Once thehead space is full, the flow rate can be reduced to match the uptakerate of the cement.

Carbon Dioxide Sensors

One or more CO₂ sensors may be used to minimize waste, i.e., to increasethe efficiency of carbon dioxide uptake, and/or to ensure worker safety.The CO₂ sensors work by measuring the CO₂ content of the air around theoutside of the mixer and/or inside the mixer. Alternatively, oradditionally, one or more sensors may be located inside the mixer andsense the carbon dioxide content of the gas in the mixer and send asignal to a controller. The sensors may be any sensor capable ofmonitoring the concentration of carbon dioxide in a gas and transmittinga signal to the controller based on the concentration, and may belocated in any convenient location or locations inside or outside themixer; if inside, preferably in a location such that the sensor is notsubject to fouling by the cement mix, e.g., hydraulic cement mix as itis being mixed or poured. In addition to, or instead of, carbon dioxidesensors inside the mixer, one or more such sensors may be locatedoutside the mixer to sense the carbon dioxide content of overflow gasescaping the mixer and send a signal to a controller. In either case, acertain range or ranges, or a cutoff value, for carbon dioxide contentmay be set, and after the carbon dioxide content of the mixer and/oroverflow gas reaches the desired range, or goes above the desiredthreshold, carbon dioxide delivery, or some other aspect of the cementmix, e.g., hydraulic cement mix apparatus, may be modulated by a signalor signals from the controller to an actuator or actuators. For example,in certain embodiments a carbon dioxide sensor may be located outsidethe mixer and when carbon dioxide content of the overflow gas reaches acertain threshold, such as a carbon dioxide concentration that indicatesthat the gas mixture in contact with the cement mix, e.g., hydrauliccement mix is saturated with carbon dioxide, carbon dioxide delivery tothe cement mix, e.g., hydraulic cement mix, e.g., inside the mixer ishalted or slowed by closing a valve, partially or completely, in theconduit from the carbon dioxide source to the mixer.

In particular, for minimizing waste, one or more sensors can be placedin the areas where leaks are most likely to occur (e.g., around doors,etc.). The sensor or sensors may be positioned so that leaking carbondioxide is most likely to pass in their vicinity, e.g., since carbondioxide is more dense than air, positioning below a likely leak point ismore desirable than positioning above a likely leak point. When the gasis delivered at a rate much greater than capacity of the cement toabsorb the CO₂ it is more likely to spill out of the mixer at a leakpoint and be detected by a gas sensor. Leaks would be a normallyoccurring event when there is too much gas delivered to the mixer giventhat the mixer is not completely gas tight according to the nature ofthe machine. A CO₂ leak would occur when the CO₂ has been delivered tooquickly. Given that CO₂ is heavier than air there would be, in general,a certain amount of CO₂ that can be delivered to the mixer wherein theincoming CO₂ gas would displace air that initial was sitting in themixer. Once the air has been displaced an delivery of additional gaswould displace previously delivered carbon dioxide or otherwise beimmediately spilled from the mixer. Sensors that feed into a dosinglogic system would preferably be placed in locations immediately besidethe mixer leak points. If the one or more sensors read that the CO₂content in the vicinity exceeds a preset threshold level (e.g. a definedbaseline), the system will adjust the CO₂ flow rate and/or deliverytime, e.g., to decrease or eliminate additional overspill in the presentbatch or to eliminate the overspill in a future mixing cycle. The logiccan co-ordinate a filling rate of the mixer space that is proportionalto the uptake rate of CO₂ by the cement.

For worker safety, if a carbon dioxide delivery causes the carbondioxide concentration in areas around the mixer normally accessed byworkers to exceed a maximum value (such as indicated by OSHA), thecontroller can signal for a system shut down wherein all the valves canbe closed and, typically, an alarm can be sounded as a safety measure.Sensors that feed into a safety system can be placed at variousdistances from the mixer depending on the proximity requirements forworkers to the mixer.

Temperature Sensors

One or more sensors may be used to monitor the temperature of the mixinside or outside of the mixer and/or of a component in contact with thecement mix, e.g., hydraulic cement mix and/or of the mixer, which isindicative of carbonation and/or other reactions due to the addition ofthe carbon dioxide, and carbon dioxide addition modulated based on thistemperature or temperatures monitored by the sensor(s). One or moretemperature sensors may be located to monitor the temperature of thecement mix, e.g., hydraulic cement mix, for example, within the mixer,or at a site distal to the mixer such as a holding site or transportsite for the cement mix, e.g., hydraulic cement mix. Such a site may be,e.g., a feedbox for a pre-cast operation, or a belt or other transportmode, or a wheelbarrow or other site for transporting or storingconcrete from a ready-mix truck. One or more temperature sensors may belocated to monitor the temperature of a component that is in contactwith the cement mix, e.g., hydraulic cement mix, e.g., the drum of themixer. Any suitable temperature sensor may be used. For example, aninfrared temperature sensor, such as a mounted or handheld sensor, maybe used to monitor the temperature of the drum of a ready-mix truck towhich carbon dioxide is added, and when a certain temperature is reachedor range of temperatures achieved, the addition of the carbon dioxideinside the drum may be modulated.

The temperature or range of temperatures at which the carbon dioxideexposure is modulated may be a predetermined temperature or range, basedon a temperature known to be associated with one or more undesirablecharacteristics, e.g., reduced strength, workability loss, poorcompactability performance, hardening in the mixer, etc. In some casesit may be an absolute temperature or range. More preferably, it is atemperature or range that is determined in reference to an initialtemperature, such as an initial temperature of the cement mix, e.g.,hydraulic cement mix or a component in contact with the mix beforeaddition of carbon dioxide. In certain embodiments, the temperature orrange is at least 10, 15, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30 35,40, 45, or 50° C. above the initial temperature, or 10-50, 10-40, 10-30°C. above the initial temperature, and with that range a threshold may beset, which may vary from batch to batch depending on the desiredcarbonation of the concrete mix or other characteristics. In certaincases, e.g., where warm starting materials are used, the temperature iskept unchanged from the starting temperature, or kept within 0-5° C. ofthe starting temperature. In some case, an absolute maximum temperatureis set and the control system is configured to keep the mix below themaximum temperature. The sensor can also be used to monitor rate oftemperature rise and the controller can adjust the flow rate and/ordelivery time if the rate is too high or too low. Test data indicatesthat, for a constant flow, the carbon uptake is proportional totemperature increase detected immediately after carbonation for a givenmix. An in-situ temperature measurement may be used to model thereal-time total carbon dioxide uptake of the cement mix, e.g., hydrauliccement mix with respect to previously collected calibration data.

Rheology Sensors

In an operation in which flowability of the cement mix is important,e.g., a wet cast operation, one or more rheology sensors may be used. Arheometer can be mounted inside the mixer to measure the workability ofthe cement mix, e.g., hydraulic cement mix. CO₂ can reduce theworkability of the fresh cement mix, e.g., hydraulic cement mix, and therheometer can be used to monitor the workability loss. At a certainpreset minimum threshold of workability, one or more actions may betriggered, such as modulation of the rate of CO₂ flow to the mixer,addition of admixture, and/or addition of additional water, to restoreworkability to a desired level. A rheometer can also monitor theworkability of concrete in a ready mix concrete truck while it is intransit and adjust CO₂/admixture doses on subsequent mixtures producedat the batching plant, or even adjust an admixture dose delivered in thedrum truck itself.

Moisture Sensors

One or more moisture sensors may be used. The moisture sensor is used tomonitor the moisture in the cement mix, e.g., hydraulic cement mixduring the mixing cycle. As CO₂ is taken up by the cement mix, e.g.,hydraulic cement mix, the apparent moisture can be reduced and result ina drier looking product. Therefore the mix moisture may need to beincreased to maintain the desired product appearance. If the moisturereaches a minimum threshold value, the CO₂ can be modulated, e.g.,reduced or shut off so the mix is not released in an unacceptably drycondition. The sensor also monitors the moisture decrease with respectto CO₂ uptake and can adjust the flow rate and/or delivery time if therate becomes too high or too low. The moisture sensor can also triggerthe addition of supplemental mix water at any point in the mixingprocess. In addition, one or more moisture sensors may be used todetermine the moisture content of one or more components of the cementmix, e.g., hydraulic cement mix before the components are mixed; forexample, a moisture sensor may be used to determine the moisture contentof aggregate, which may be exposed to weather conditions leading towater pickup. In the case of an operation where carbon dioxide is addedvia mix water as well as by gas or liquid, such information may be usedto adjust the relative amount of carbon dioxide added via gas or liquid,to compensate for the fact that less mix water will be used due to themoisture content of the aggregate.

Other Sensors

One or more sensors may monitor conditions of the cement mix, e.g.,hydraulic cement mix apparatus and send a signal to a controller. Forexample, one or more sensors may monitor when all desired components ofthe cement mix, e.g., hydraulic cement mix are in the mixer and mixing,and the controller may send a signal to an actuator, such as acontrollable valve, to begin flow of carbon dioxide. The carbon dioxideflow may continue for a predetermined time, or may be modulatedaccording to further feedback, such as described above.

Other conditions may be monitored, as well, such as pressure conditionsin one or more lines; for example, in a system where liquid carbondioxide is delivered to the mixer, sensors may be employed to controldry ice formation between the nozzle and solenoid as well as to confirmpre-solenoid pressure is maintained to ensure the line remains liquid.

Any combination of one or more sensors inside or outside the mixer,and/or inside or outside the mix, may be used to monitor cement binderweight, cement binder location, carbon dioxide content, temperature,rheology, moisture content, pH, other characteristics, or a combinationthereof, and feedback loops to modulate the addition of carbon dioxidebased on the information provided by these sensors may be used; suchloops may include automatic or manual adjustments, or both. In certainembodiments, sensors monitor the cement binder addition time and/or dustcollector system operation time, as in some mixers a fan is run afterthe powders go in to prevent excessive dust, and these should be turnedoff so that added carbon dioxide is not removed during this time.

Thus, in certain embodiments the invention provides a method orapparatus for producing carbonated cement mix, e.g., hydraulic cementmix that includes a control system that includes at least one sensorselected from the group consisting of a carbon dioxide sensor, atemperature sensor, a rheology sensor, and a moisture sensor. In certainembodiments the invention provides a method or apparatus for producingcarbonated cement mix, e.g., hydraulic cement mix that includes acontrol system that includes at least two sensors selected from thegroup consisting of a carbon dioxide sensor, a temperature sensor, arheology sensor, and a moisture sensor. In certain embodiments theinvention provides a method or apparatus for producing carbonated cementmix, e.g., hydraulic cement mix that includes a control system thatincludes at least three sensors selected from the group consisting of acarbon dioxide sensor, a temperature sensor, a rheology sensor, and amoisture sensor. In certain embodiments the invention provides a methodor apparatus for producing carbonated cement mix, e.g., hydraulic cementmix that includes a control system that includes a carbon dioxidesensor, a temperature sensor, a rheology sensor, and a moisture sensor.The methods and apparatus can further include one or more actuators foradjusting some aspect of the mix operation, for example carbon dioxideflow to the mixer, or admixture flow to the mixer, and a controller thatreceives signals from the sensor or sensors, processes them to determineif modulation of the mix operation is required, and, if so, transmits asignal to an actuator or actuators to carry out the modulation.

Actuators

The actuator or actuators may be, e.g., one or more valves, such assolenoid valve, in one or more conduits supplying a component, such ascarbon dioxide, to the mixer, as described elsewhere herein. An actuatorfor CO₂ delivery can be, e.g., a delivery manifold with, e.g. gastemperature sensor, gas pressure gauge, modulating control valve,open/close solenoid and orifice plate assembly. These components can allbe combined in a singular unit, i.e. a flow controller. In certainembodiments, in addition to or alternatively to, a gas delivery system,one or more actuators for controlling delivery of carbonated mix water,as described herein, may be used. Such actuators may include, e.g.,actuators to control charging mix water with carbon dioxide and/oractuators to control delivery of carbon dioxide-charged water to themixer. Similarly, an actuator controlling water delivery to the mix maybe under the control of the controller, as may be an actuatorcontrolling delivery of one or more admixtures to the mix. In addition,an actuator may include a relay switch attached to dust collector powersource to shut off mixer dust collector during CO₂ delivery (ifnecessary). In general, the modulation of the carbon dioxide exposurewill be an increase or decrease in exposure, such as a decrease in flowrate of carbon dioxide gas to the mixer. In certain embodiments, themodulation is halting the flow of carbon dioxide gas to the mixer.

Thus, in certain embodiments the invention provides a method orapparatus for producing carbonated cement mix, e.g., hydraulic cementmix that includes a control system that includes at least one actuatorfor controlling at least one action selected from the group consistingof a carbon dioxide flow to the mixer, water flow to the mixer, andadmixture flow to the mixer. In certain embodiments the inventionprovides a method or apparatus for producing carbonated cement mix,e.g., hydraulic cement mix that includes a control system that includesat least two actuators for controlling at least two actions selectedfrom the group consisting of a carbon dioxide flow to the mixer, waterflow to the mixer, and admixture flow to the mixer. In certainembodiments the invention provides a method or apparatus for producingcarbonated cement mix, e.g., hydraulic cement mix that includes acontrol system that includes an actuator for controlling carbon dioxideflow to the mixer, an actuator for controlling water flow to the mixer,and an actuator for controlling admixture flow to the mixer.

Other actuators, such as actuators that control one or more aspects ofhydraulic cement production, such as timing of mixing, delivery ofcooling input such as ice or liquid nitrogen, activation of an alarm,and the like, may also be used as appropriate.

Controller

The control systems used in methods and apparatus can include acontroller that receives inputs from the one or more sensors, processesthem by comparing them to preset values for achieving the desiredresult, and, as necessary, sends outputs to the one or more actuators tomove the system toward the desired result.

The controller may be, e.g., an electronic circuit or a programmablelogic controller, located either on-site with the mixer or off-site,e.g., as part of a computer network. For example, the controller may bea Programmable Logic Controller (PLC) with a Human Machine Interface(HMI), for example a touch screen and onboard telemetry computer. Thecontroller can be integrated into the overall mixer controller or it canbe a separate unit that receives inputs from the mixer controller asappropriate.

An exemplary set of operations for a controller in response to inputsfrom various sensors and giving outputs to various actuators isillustrated below.

The system can include the following components: 1) Programmable LogicController (PLC) with attached Human Machine Interface (HMI), forexample a touch screen and onboard telemetry computer. 2) Gas deliverymanifold with, e.g., gas temperature sensor, gas pressure gauge,modulating control valve, open/close solenoid and orifice plateassembly. These components can all be combined in a singular unit, i.e.a flow controller. 3) Cement weight scale feeding into a concrete mixerto measure quantity of cement used in a batch. This quantity is usedlogically to determine the CO₂ dose based on cement content (furtherinformation below). 4) Proximity switch to trigger the delivery of CO₂into the mixer 5) Relay switch attached to dust collector power sourceto shut off mixer dust collector during CO₂ delivery (if necessary). 6)One or more CO₂ sensors positioned around the mixer used to monitorcarbon dioxide gas concentration outside the mixer. The data can be usedlogically to minimize wastage by controlling flow or monitor safety(further information below). 7) Concrete temperature sensor in or onmixer used to monitor the concrete temperature during the carbonationtreatment. The data can be used logically to control the CO₂ dose aswell as the flow rate (further information below). 8) Moisture sensorused to monitor concrete moisture in the mixer. This information can beused to logically control the CO₂ dose (further information below). 9)Concrete rheology sensor to monitor the consistency of the concrete.Information about the workability of the concrete can logically be usedto signal admixture delivery or process end points. Not all of thesecomponents need be present, depending on the needs of the mix operation.For example, in a dry cast operation, a rheology sensor may not be used.

The steps of operation of the system are as follows:

1. A PLC is programmed, for example, through the HMI, to apply carbondioxide treatment to a first batch. Process threshold settings foraspects such as CO₂ concentration in the air at a leak point and/or at aworker area, concrete temperature and/or rate of temperature change,concrete moisture and/or rate of moisture change, concrete rheology canbe input at this time.

2. Batching starts by a signal from the mixing controller to the mixer.This follows logically after the previous step. The mixer controllersoftware can communicate batch information to the PLC.

3. Materials are added to mixer (e.g. aggregates). This followslogically after the previous step as part of normal practice.

4. The cement is weighed. This follows logically after the previous stepas part of normal practice. A cement mass (weight) sensor determinesmass (weight) of cement used in the batch and feeds information to thePLC

5. The PLC makes a calculation to determine the required gas flow. Thisfollows logically from an earlier step. The PLC calculates the amount ofgas required for delivery to the current mix based upon a percentagedosage rate of gas mass to cement mass. The PLC calculation may refer toa predetermined set point. It may alternatively, or in addition, callupon historical data of previous combinations of mix size, mix type andCO₂ dosage rate, either from the mix site at which the current batch isbeing mixed, or from other mix sites, or a combination thereof. It canuse information (either input or detected) about the batch size, cementmass, mix type and mixer volume. For example, it can use informationabout cement type or origin to determine whether, which, and/or how muchadmixture should be employed. The PLC can accept information requiredfor calculations from sources including user input into the HMI,communication with the mixer controller software, and the cement masssensor. The PLC calculations will depend upon acquiring all of therequired data which can come from, e.g., the HMI in step 1, mixcontroller software in step 2, and/or the cement mass sensor in step 4.

6. Cement is dropped into the mixer. This follows logically after theprevious step. The time that cement enters the mixer is detected. Aproximity sensor can detect the cement deposit in the mixer through aphysical movement (e.g. the opening of a door or gate). Alternatively,the cement addition time can be supplied synchronously from the mixercontroller software. The time that the cement is placed into mixer istransmitted to the PLC.

7. The PLC starts the gas delivery. This can be concurrent with theprevious step, at some predetermined time after the previous step, oreven before the previous step, if it is desired to replace some or allof the air in the mixer with CO₂ prior to deposition of the cement. ThePLC can send a signal to the mixer dust collector to be turned off forall or part of the CO₂ delivery or otherwise coordinated with someaspect of the gas delivery. The PLC sends signal to the solenoid in theCO₂ delivery system to open either in coordination with the cementinsertion or at some time before or after the insertion.

8. The PLC surveys the sensors for any process conditions that signalthe CO₂ delivery is to change/end according to preset conditions or forother measurable aspects. This follows logically after the previousstep. A) Temperature sensor—the concrete temperature exceeds a thresholdvalue or rate that can be set for correlation to a maximum allowabletemperature rise or a target temperature rise. B) CO₂ leak sensors—theCO₂ sensors at the significant leak points of the mixer have detected aCO₂ content that exceeds a preset threshold or a relative value above abaseline measurement. C) CO₂ safety sensors—the CO₂ sensors monitoringthe CO₂ content of the air in the general vicinity of the mixer havereached a threshold value. There can also be an oxygen sensor measuringthe oxygen content of the air. These sensors are located in areasaccessed by workers around the machine as opposed to leaks immediatelyfrom the mixer. D) Moisture sensor—the moisture content of the concretehas reached an absolute threshold with respect to a set point orotherwise has passed a relative measure with respect to the batch athand. For example, a condition might acknowledge that the moisturecontent of the concrete inherently varies from batch to batch but wouldsearch for a decline in moisture content of, e.g., 0.5% with respect tothe measurement expected if no CO₂ had been applied or the initialmeasurement, etc. E) Rheology—(relevant to wet mix) the workability ofthe concrete is measured and found to reach a threshold level. F) Timeron PLC—PLC may have a predefined maximum delivery time that may signal astop condition in the event no other sensors have triggered a stop.

9. A gas flow modification condition is detected. The PLC receives asignal from a sensor and modifies the gas delivery in response. Followslogically from previous step. A) Any sensor may suggest the gas inputflow is modified (e.g., reduced) as a threshold value is neared ratherthan simply attained or crossed. B) Temperature Sensor—if the sensordetects an increase in the temperature of the concrete that is greaterthan expected then a signal can be sent by the PLC to reduce the rate ofinput of carbon dioxide. Conversely, if the rate of temperature increaseis lower than expected then the PLC can increase the rate input ofcarbon dioxide. In addition or alternatively, if a certain thresholdtemperature is reached, carbon dioxide delivery may be halted. C) CO₂leak sensors—if the sensors detect an increase in CO₂ concentration atthe mixer leak points a signal can be sent to the PLC, which reduces theinput of carbon dioxide. For example, the leaking can be an indicationthat the head space of the mixer has been filled with CO₂ and anyfurther addition will result in leaks or overspill. The CO₂ input may bereduced to a rate that is in proportion to the projected absorption rateof the carbon dioxide into the cement. Thereby any gas that is absorbedinto the concrete is in turn replaced with new gaseous CO₂ to maintainan overall amount of gas in the mixer. D) Rheology sensor—if the sensordetects a decrease, e.g., a rapid decrease in the workability of theconcrete, a signal can be sent by the PLC to reduce carbon dioxideinput. Conversely, if the workability loss is less than expected, thePLC can increase the carbon dioxide input. Other outputs from the PLCmay cause addition of admixture, water, or both to the mix.

10. A gas delivery stop condition achieved, PLC receives signal to stopgas delivery. Follows logically from previous step. Solenoid is closed.Gas delivery ends.

11. After the CO₂ delivery is complete the sensors may send signals tothe controller that call for supplemental inputs to the mixer. Followslogically from previous step. A) Temperature sensor can detect atemperature rise that calls for the concrete temperature to be reducedthrough the addition of a cooling input such as ice or liquid nitrogen.B) Temperature sensor detects that the target CO₂ uptake of the concretehas been achieved which may prompt the addition of an appropriateadmixture. C) Moisture sensor reading causes PLC to signal foradditional mix water or other remedial measure such as an admixture. D)Rheology sensor input to PLC causes output for additional mix wateraddition, or an admixture addition, or both, to facilitate a workabilityincrease or other remedial measure.

12. Batching and mixing is complete. Concrete is released to theremainder of the production cycle. Follows logically from previous step.

13. The PLC can perform calculations to learn for subsequentbatches—particularly for the next time that same or similar combinationof mix design and CO₂ dosage is used. Otherwise settings can bepredicted for other CO₂ dosages to apply to that same mix design, or forsmaller batches of that mix design with the same CO₂ dosage, etc. Thiscan be concurrent with previous step. A) The data from CO₂ leak sensorscan dictate that, for a future mix, the flow rate should be reduced ifthere were excessive leaks (too much gas is supplied) or increasedbecause there are no leaks at all (not enough gas has been supplied) inthe present mix. The PLC will make note of the updated or recalculatedgas flow setting for future use. B) Temperature data can inform futurecooling treatment usage. The PLC will make note of the temperatureresponse in the wake of the applied temperature adjustment foradjustment of the cooling treatment in future batches. For example thefuture cooling treatment can be greater or lower if the current coolingtreatment was found to be inadequate. C) Temperature data can informfuture kinetic assessments of temperature rise vs time for a givencombination of mix design and gas delivery condition. D) The moisturesensor data can inform future mix water adjustment required either to beincluded as part of the initial mix water or as late addition mix water.In the first case the total water addition might be approachedincrementally whereas later mixes can use the end point determined inthe first mix as a target setting. E) Rheological information can informfuture admix usage. The PLC can correlate a quantified dose of admixwith the response in workability metric. The proportion of admix toaspects such as, but not limited to, cement content, absorbed carbondioxide (either measured directly after the fact or approximated bytemperature increase) workability improvement can be recorded andrecursively recalculated as additional data is acquired therebyimproving the admix dosing logic. Further information regardingcharacteristics of the batch, such as flowability or strength at one ormore time points, water absorption, and the like, may also be input.

14. Telemetry data can be logged and distributed by the PLC to a remotedata storage. This can be concurrent with the end of gas delivery (step10) or follow from later steps if additional information acquired afterthe end of delivery is part of the transmitted information.

Exemplary mixers and control systems are illustrated in FIGS. 1, 2, and3. FIG. 1 shows a stationary planetary mixer, e.g., for use in a precastoperation. The cement scale 1 includes a mass sensor that sends dataregarding the mass of cement dispensed from the cement silo 2 to thecontroller 10. Proximity sensor 3 senses when cement is released to themixer and sends a signal to the controller; alternatively, the mixcontroller (not shown) can send a signal to the controller 10 when thecement is released. CO₂ delivery may commence upon release of thecement; alternatively, CO₂ delivery may commence before or afterrelease. CO₂ sensors 8 and 9 are located at leak areas outside the mixerand send signals regarding atmospheric CO₂ content to the controller 10.In addition, temperature sensor 6 sends signals regarding thetemperature of the concrete mix to the controller 10. Additionalsensors, such as moisture and rheology sensors, or additional CO₂sensors in worker areas in the vicinity of the mixer may be used (notshown) and send additional signals to the controller. Controller 10processes the signals and sends output to an actuator 11 for controllingdelivery of CO₂ from a CO₂ supply 13 via a conduit to the CO₂ gas mixerinlet 7, where it enters the mixer headspace 4 and contacts the mixingconcrete 5. For example, in a basic case, the controller 10 may send asignal to the actuator 11 to open a valve for delivery of CO₂ uponreceiving input from the proximity sensor 3 indicating that cement hasbeen delivered to the mixer, and send a signal to the actuator 11 toclose the valve upon receiving input from one or more of the CO₂ sensors8 and 9 or the temperature sensor 6 indicating that the desired deliveryof CO₂ to the mixer, or uptake of CO₂ into the concrete has beenachieved. The controller may send output to additional actuators such asan actuator for controlling water addition or an actuator controllingadmixture addition (not shown). An optional telemetry may be used totransmit information regarding the batch to a central location to beused, e.g., to store data for use in future batches and/or to use formodification of the same or similar mixes in other locations.

FIGS. 2 and 3 show a mobile cement mixer, in this case, a ready mixtruck. FIG. 2 shows a ready mix truck 1 with a detachable carbon dioxidedelivery system. Carbon dioxide is supplied from a carbon dioxide supply8 via a conduit that is attachable to a conduit on the truck 2 at ajunction 4. Controller 6 controls the supply of carbon dioxide to thedrum of the truck 2 via an actuator 5. Sensors, such as CO₂ sensors maybe located at leak areas outside and/or inside the drum 2 and sendsignals regarding atmospheric CO₂ content to the controller 6. Inaddition, one or more temperature sensors may sends signals regardingthe temperature of the concrete mix to the controller 6. Additionalsensors, such as moisture and rheology sensors, or additional CO₂sensors in worker areas in the vicinity of the mixer may be used (notshown) and send additional signals to the controller. The controllerssends a signal to the actuator (e.g., valve) 5 to control addition ofcarbon dioxide to the drum 2. Additional actuators may be controlled bythe controller, such as to control addition of an admixture to the drum2. An optional telemetry system 7 may be used to transmit informationregarding the batch to a central location to be used, e.g., to storedata for use in future batches and/or to use for modification of thesame or similar mixes in other locations. FIG. 3 shows a ready mix truckwith attached carbon dioxide delivery system that travels with the truck1. This can be useful to, e.g., optimize exposure of the cement mix tocarbon dioxide. Carbon dioxide is supplied from a carbon dioxide supply7 via a conduit 3 that is attachable the truck and delivers carbondioxide to the drum of the truck 2. Controller 5 controls the supply ofcarbon dioxide to the drum of the truck 2 via an actuator 4. Sensors,such as CO₂ sensors may be located at leak areas outside and/or insidethe drum 2 and send signals regarding atmospheric CO₂ content to thecontroller 5. In addition, one or more temperature sensors may sendssignals regarding the temperature of the concrete mix to the controller5. Additional sensors, such as moisture and rheology sensors, oradditional CO₂ sensors in worker areas in the vicinity of the mixer maybe used (not shown) and send additional signals to the controller. Thecontrollers sends a signal to the actuator (e.g., valve) 4 to controladdition of carbon dioxide to the drum 2. Additional actuators may becontrolled by the controller, such as to control addition of anadmixture to the drum 2. An optional telemetry system 6 may be used totransmit information regarding the batch to a central location to beused, e.g., to store data for use in future batches and/or to use formodification of the same or similar mixes in other locations. In certainembodiment the controller 5 is located remote from the truck andreceives the signals from the telemetry system, and transmits signalswhich are received and acted upon by the actuator 4.

D. Mixers

The mixer in which the carbon dioxide is contacted with the cement mix,e.g., hydraulic cement mix during mixing may be any suitable mixer. Themixer may be relatively fixed in location or it may provide both mixingand transport to a different location from the mixing location.

In certain embodiments, the mixer is fixed or relatively fixed inlocation. Thus, for example, in certain embodiments the mixer is part ofa pre-casting apparatus. For example, the mixer may be configured formixing concrete before introducing the concrete into a mold to produce aprecast concrete product. In certain embodiments, the mixer isconfigured to mix concrete before introducing the concrete into a mold,and the addition of carbon dioxide to the concrete mix, the componentsof the concrete mix, and, optionally, other ingredients such as one ormore admixtures, are adjusted so that a desired level of flow of theconcrete mix, generally very low or no flow, is combined with a desiredlevel of compactability so that the concrete may be compacted within acertain range of parameters during and after delivery to a mold, and sothat the final product possesses a desired hardening time, strength,shrinkage, and other characteristics as desired. For example, a gas tubeto deliver carbon dioxide into the mixer may be placed with the gas linepositioned in such a way that it does not interfere with the normalmixer operation. Gas is delivered in proportion to the amount of cement,for example in the range 0.5% to 2.5%, or any other suitable range asdescribed herein. The gas delivery can be confined to the normal mixingtime. In certain embodiments gas delivery may be triggered by a gate forthe cement addition pipe. When the gate closes (signaling completion ofcement addition) a magnetic proximity sensor detects the closed stateand triggers the start of the carbon dioxide flow.

In certain embodiments in which the mixer is a fixed mixer, for examplein a dry cast or wet cast pre-casting operation, the mixer is configuredto mix concrete and to deliver it to a holding component, e.g., ahopper, which further delivers the concrete to a mold, optionally via afeedbox. Additional carbon dioxide can be added to the cement mix, e.g.,hydraulic cement mix at the hopper and/or feedbox, if desired. See U.S.patent application Ser. No. 13/660,447 incorporated herein by referencein its entirety. In certain embodiments, no further carbon dioxide isadded to the mix (apart from carbon dioxide in the atmosphere) after theconcrete exits the mixer.

The addition of carbon dioxide may affect the compactability and thusthe strength of the final object, e.g., precast object. In the case of awet cast operation, flowability is also a consideration. Thus, incertain embodiments, the addition of carbon dioxide to the concrete mix,the components of the concrete mix, and, optionally, other ingredientssuch as one or more admixtures, are adjusted so that a desired level ofcompactability (strength) and/or flowability of the cement mix, e.g.,hydraulic cement mix, e.g., concrete, is achieved, generally a level ofcompactability (strength) and/or flowability similar to the level thatwould be present without the addition of the carbon dioxide, so that thefinal product after the concrete is poured into the mold and compactedat possesses a desired strength, such as a desired 1-, 7-, 28 and/or56-day strength, and/or so that the flowability is at a desired value.In the case of the pre-cast mixer, the addition of carbon dioxide,components of the concrete mix, and/or additional components such as oneor more admixtures, may be adjusted so that compactability and/or 1-,7-, 28 and/or 56-day strength of the final concrete mix is within 50,40, 30, 20, 10, 8, 5, 4, 3, 2, 1, 0.5, or 0.1% of the value or valuesthat would be achieved without the addition of carbon dioxide, or iswithin 50, 40, 30, 20, 10, 8, 5, 4, 3, 2, 1, 0.5, or 0.1% of apredetermined desired value. In certain embodiments, the addition ofcarbon dioxide, components of the concrete mix, and/or additionalcomponents such as one or more admixtures, may be adjusted so thatcompactability and/or 1-, 7-, and/or 28-day strength of the finalconcrete mix of the final concrete mix is within 10% of thecompactability and/or 1-, 7-, and/or 28-day strength of the finalconcrete mix that would be achieved without the addition of carbondioxide. In certain embodiments, the addition of carbon dioxide,components of the concrete mix, and/or additional components such as oneor more admixtures, may be adjusted so that compactability and/or 1-,7-, and/or 28-day strength of the final concrete mix is within 5% of thecompactability and/or 1-, 7-, and/or 28-day strength of the finalconcrete mix that would be achieved without the addition of carbondioxide. In certain embodiments, the addition of carbon dioxide,components of the concrete mix, and/or additional components such as oneor more admixtures, may be adjusted so that compactability and/or 1-,7-, and/or 28-day strength of the final concrete mix is within 2% of thecompactability and/or 1-, 7-, and/or 28-day strength of the finalconcrete mix that would be achieved without the addition of carbondioxide. Other limits and ranges of compactability and/or 1-, 7-, and/or28-day strength of the final concrete mix, as described herein, may alsobe used. Any suitable measurement method for determining compactabilityand/or 1-, 7-, and/or 28-day strength of the final concrete mix may beused. In certain embodiments, in addition to the desired compactabilityand/or 1-, 7-, and/or 28-day strength of the final concrete mix, one ormore additional characteristics are achieved, such as that shrinkage iswithin certain desired ranges, or above or below certain thresholdnumbers, as determined by standard methods in the art. In all cases, ifthe operation is a wet cast operation, additionally, or alternatively,flowability may be modulated, e.g., by use of one or more admixtures,for example so that flowability is within 50, 40, 30, 20, 10, 8, 5, 4,3, 2, 1, 0.5, or 0.1% of the value or values that would be achievedwithout the addition of carbon dioxide, or within 50, 40, 30, 20, 10, 8,5, 4, 3, 2, 1, 0.5, or 0.1% of a predetermined value. Any suitableadmixture, as described herein, may be used. In certain embodiments theadmixture comprises a set retarder. In certain embodiments, theadmixture comprises a carbohydrate, such as a saccharide, e.g., a sugaror sugar derivative. In certain embodiments, the admixture is selectedfrom the group consisting of fructose, sodium glucoheptonate, and sodiumgluconate. In certain embodiments, the admixture is sodium gluconate,e.g., sodium gluconate delivered to achieve a percentage, per weight ofcement, of 0.05-0.8%, 0.1-0.8%, or 0.1-0.6%, or 0.1-0.5%, or 0.2-0.5%,or 0.2-3%, or 0.2-2%, or 0.2-1%. In certain embodiments a secondadmixture is also used, such as any of the admixtures described herein.

In certain embodiments, the mixer is a transportable mixer.“Transportable mixer,” as that term is used herein, includes mixers intowhich components of a cement mix, e.g., hydraulic cement mix are placedin one location and the cement mix, e.g., hydraulic cement mix istransported to another location which is remote from the first location,then used. A transportable mixer is transported by, for example, road orrail. As used herein, a transportable mixer is not a mixer such as thoseused in a pre-cast concrete operations. Thus, in certain embodiments,the mixer may be the drum of a ready-mix truck in which a concrete mixis prepared for delivery to a worksite. In this case, the mixer isconfigured to mix concrete and to deliver it to a worksite, and theaddition of carbon dioxide to the concrete mix, the components of theconcrete mix, and, optionally, other ingredients such as one or moreadmixtures, are adjusted so that a desired level of flow of the cementmix, e.g., hydraulic cement mix, i.e., concrete, generally a level offlow that is similar to the level that would be present without theaddition of the carbon dioxide, or a predetermined flowability, isachieved, and so that the final product after pouring at the worksitepossesses a desired hardening time, strength, shrinkage, and othercharacteristics as desired. In the case of the ready-mix mixer, theaddition of carbon dioxide, components of the concrete mix, and/oradditional components such as one or more admixtures, may be adjusted sothat flowability of the final concrete mix is within 50, 40, 30, 20, 10,8, 5, 4, 3, 2, 1, 0.5, or 0.1% of the flowability that would be achievedwithout the addition of carbon dioxide, or a predetermined flowability.In certain embodiments, the addition of carbon dioxide, components ofthe concrete mix, and/or additional components such as one or moreadmixtures, may be adjusted so that flowability of the final concretemix is within 10% of the flowability that would be achieved without theaddition of carbon dioxide, or a predetermined flowability. In certainembodiments, the addition of carbon dioxide, components of the concretemix, and/or additional components such as one or more admixtures, may beadjusted so that flowability of the final concrete mix is within 5% ofthe flowability that would be achieved without the addition of carbondioxide, or a predetermined flowability. In certain embodiments, theaddition of carbon dioxide, components of the concrete mix, and/oradditional components such as one or more admixtures, may be adjusted sothat flowability of the final concrete mix is within 2% of theflowability that would be achieved without the addition of carbondioxide, or a predetermined flowability. Other limits and ranges offlowability, as described herein, may also be used. Any suitablemeasurement method for determining flowability may be used, such as thewell-known slump test. In certain embodiments, in addition to thedesired flowability, one or more additional characteristics areachieved, such as that shrinkage and/or strength, such as compressivestrength, at one or more times after pouring of the concrete are withincertain desired ranges, or above or below certain threshold numbers, asdetermined by standard methods in the art. The addition of carbondioxide, components of the concrete mix, and/or additional componentssuch as one or more admixtures, may be adjusted so that 1-, 7-, 28,and/or 56-day strength of the final concrete mix is within 50, 40, 30,20, 10, 8, 5, 4, 3, 2, 1, 0.5, or 0.1% of the value or values that wouldbe achieved without the addition of carbon dioxide, or a predeterminedstrength value.

It will be appreciated that, depending on the mix design, dose of carbondioxide, and/or other aspects of the mix or conditions under which theconcrete is mixed and/or used, the carbonated concrete may have agreater compressive strength at one or more time points compared touncarbonated concrete; this is especially likely when a low dose ofcarbon dioxide is used, such as a dose of less than 1% bwc (see Low Dosesection. In this case, the addition of a particular dose of carbondioxide may result in an increase in strength, e.g., compressivestrength, such as an increase of at least 1, 2, 3, 4, 5, 7, 10, 15, 20,30, 40, or 50% compared to uncarbonated concrete of the same mix designand under the same conditions at one or more times after mixing, such asat 24 hours, 3 days, 7 days, 28 days, 56 days, or the like;alternatively, or additionally, the amount of cement in the mix may bereduced so that the carbonated mix contains less cement than theuncarbonated mix but reaches an acceptable compressive strength at oneor more desired times after mixing, such as within 20, 10, 5, 4, 3, 2,or 1% of the compressive strength of an uncarbonated mix with the normalamount of cement. In certain embodiments, the amount of cement in themix may be reduced by at least 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 15,20, 25, or 30% compared to uncarbonated mix and still achieve thedesired strength at the desired time(s). These considerations ofincreased strength and/or decreased use of cement apply to bothtransportable and stationary operations. In certain embodiments, theaddition of carbon dioxide, components of the concrete mix, and/oradditional components such as one or more admixtures, may be adjusted sothat 1-, 7-, 28, and/or 56-day strength of the final concrete mix of thefinal concrete mix is within 10% of the 1-, 7-, 28 and/or 56-daystrength of the final concrete mix that would be achieved without theaddition of carbon dioxide, or a predetermined strength value. Incertain embodiments, the addition of carbon dioxide, components of theconcrete mix, and/or additional components such as one or moreadmixtures, may be adjusted so that 1-, 7-, 28 and/or 56-day strength ofthe final concrete mix is within 5% of the 1-, 7-, 28 and/or 56-daystrength of the final concrete mix that would be achieved without theaddition of carbon dioxide, or a predetermined strength value. Incertain embodiments, the addition of carbon dioxide, components of theconcrete mix, and/or additional components such as one or moreadmixtures, may be adjusted so that 1-, 7-, 28 and/or 56-day strength ofthe final concrete mix is within 2% of the 1-, 7-, 28 and/or 56-daystrength of the final concrete mix that would be achieved without theaddition of carbon dioxide, or a predetermined strength value. Otherlimits and ranges of 1-, 7-, 28 and/or 56-day strength of the finalconcrete mix, as described herein, may also be used. Any suitablemeasurement method for determining 1-, 7-, 28 and/or 56-day strength ofthe final concrete mix may be used. In certain embodiments, in additionto the desired 1-, 7-, 28 and/or 56-day strength of the final concretemix, one or more additional characteristics are achieved, such as thatshrinkage is within certain desired ranges, or above or below certainthreshold numbers, as determined by standard methods in the art.

In embodiments in which an admixture is used, any suitable admixture, asdescribed herein, may be used. In certain embodiments the admixturecomprises a set retarder. In certain embodiments, the admixturecomprises a carbohydrate, such as a saccharide, e.g., a sugar. Incertain embodiments, the admixture is selected from the group consistingof fructose, sodium glucoheptonate, and sodium gluconate. In certainembodiments, the admixture is sodium gluconate, e.g., sodium gluconateat a percentage of 0.01-2%, or 0.01-1%, or 0.01-0.8%, or 0.01-0.5%, or0.01-0.1%, or 0.1-0.8%, or 0.1-0.6%, or 0.1-0.5%, or 0.2-0.5%, or0.2-3%, or 0.2-2%, or 0.2-1%. In certain embodiments, the admixture isfructose, e.g., fructose at a percentage of 0.01-2%, or 0.01-1%, or0.01-0.8%, or 0.01-0.5%, or 0.01-0.1%, or 0.1-0.8%, or 0.1-0.6%, or0.1-0.5%, or 0.2-0.5%, or 0.2-3%, or 0.2-2%, or 0.2-1%. In certainembodiments a second admixture is also used, such as any of theadmixtures described herein.

One type of transportable mixer is a volumetric truck. A volumetricconcrete truck is a truck that carries and mixes concrete onsite bymixing aggregate, cement and water at the job site, generally by using abelt to measure the ingredients and an auger to mix the concrete beforedischarging. A schematic of a truck can be seen in FIG. 147. As seen inFIG. 147, the concrete is mixed in an auger and then discharged. Thisauger is in a trough and is typically covered with a rubber mat. Thus,in this embodiment, the mixer is the augur, and CO₂ gas or gas/solid canbe added to the mixing concrete from the top of the auger through aconduit. The rubber roof keeps the CO₂ enclosed in the trough and allowsit to mix with the concrete before discharge. The CO₂ can be controlledby, e.g., using a flow meter and a solenoid. The system can becontrolled manually, using a knob on the flow meter and manually openingthe solenoid. It can also be controlled automatically by, e.g., gettinga signal from the truck computer that corresponds to the rate at whichcement is being metered into the mixing hopper and be triggered when theauger is moving. The source of carbon dioxide can be any source asdescribed herein, for example, a liquid tank or a gas tank. In thelatter case, a high pressure CO₂ cylinder can be mounted on the truck inorder to supply the CO₂ for the concrete. The cylinder may also beheated (using a heating jacket) if the flow rate needed exceeds thatpossible by the natural boiling inside the cylinder. These trucks can doup to 60 m³/hr (1 m³/min), but typically only carry enough material for˜8 m³ of concrete. This would mean a maximum CO₂ flow rate between60-500 SLPM depending on cement content of the mix and CO₂ dose. Otheraspects are as described above for transportable mixers.

It will be appreciated that, both in the case of a wet cast (such asreadymix) or a dry cast, different mixes may require different treatmentin order to achieve a desired flowability and/or compactability, andthat mix types may be tested in advance and proper treatment, e.g.,proper type and/or percentage of admixture determined. In certain casesadmixture may not be required; indeed, with certain mix types and carbondioxide concentrations, compactability (strength) or flowability may bewithin acceptable limits; e.g., strength may even be improved in certainmix types at certain levels of carbon dioxide addition. Also, the pointin the procedure in which ingredients are introduced can affect one ormore characteristics of the product, as can be determined in routinetesting and mix adjustment.

The mixer may be closed (i.e., completely or substantially completelyairtight) or open (e.g., the drum of a ready mix truck, or a precastmixer with various leak points). The mixer may be one of a plurality ofmixers, in which different portions of a cement mix, e.g., hydrauliccement mix are mixed, or it may be a single mixer in which the entirecement mix, e.g., hydraulic cement mix, such as a concrete mix, exceptin some cases additional water, is mixed.

Methods of Carbon Dioxide Delivery

Any suitable mixer for mixing concrete in an operation to produceconcrete for use in objects, such as for use in producing buildingmaterials, may be used. In some cases a mixer may be used where thedesired dose or uptake of carbon dioxide may be achieved using gasdelivery alone. For example, in most pre-cast mixers, the mixer isenclosed but not gas-tight (i.e., not open to the atmosphere, althoughnot gas tight, such that leak points are available for, e.g., carbondioxide sensors) and the head space and mixing times are such that adesired dose or uptake can be achieved with nothing more than gaseouscarbon dioxide delivery.

In some cases, however, such as in a ready mix truck where head space isrelative less than in a typical precast mixer, additional efficiency maybe desired, or necessary, in order to achieve a desired carbon dioxidedose or uptake. In these cases, the use of carbon dioxide-charged mixwater, or liquid carbon dioxide delivered so as to form a gas and asolid, or addition of solid carbon dioxide, or any combination thereof,may be used. The carbon dioxide may be delivered to the mixer as aliquid which, through proper manipulation of delivery, such as flow rateand/or orifice selection, becomes a mixture of gaseous carbon dioxideand solid carbon dioxide upon delivery, for example, in an approximate1:1 ratio. The gaseous carbon dioxide is immediately available foruptake into the cement mix, e.g., hydraulic cement mix, while the solidcarbon dioxide effectively serves as a time-delayed delivery of gaseouscarbon dioxide as the solid gradually sublimates to gas. Additionally,or alternatively, carbon dioxide-charged mix water may be used. Carbondioxide-charged water is routinely used in, e.g., the soda industry, andany suitable method of charging the mix water may be used. The water maybe charged to achieve a carbon dioxide concentration of at least 1, 2,3, 4, 5, 6, 7, 8, 9, or 10 g CO₂/L water. Carbon dioxide-charged mixwater can deliver a significant portion of the desired carbon dioxidedose for a cement mix, e.g., hydraulic cement mix, for example, at least5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90,or 95% of the total carbon dioxide delivered to a batch of cement mix,e.g., hydraulic cement mix may be delivered in the mix water. In somecases, 100% of the carbon dioxide may be delivered in the mix water. Insome cases, at least 20% of the carbon dioxide is delivered in the mixwater. In some cases, at least 30% of the carbon dioxide is delivered inthe mix water. Without being bound by theory, it is thought that thecarbon dioxide thus delivered reacts rapidly with components of thecement mix, e.g., hydraulic cement mix, allowing further uptake ofgaseous carbon dioxide by the water. Carbon dioxide may also bedelivered in solid form, i.e., as dry ice, directly, as describedelsewhere herein.

A ready mix operation is an example of a system where it may bedesirable to use one or both of carbon dioxide-charged water and liquidcarbon dioxide delivery. A ready mix truck drum is open to theatmosphere and has a relatively small head space in comparison to themass of concrete, which is typically 6 to 10 cubic meters when the truckis batched to capacity, which it is as often as possible. Mixing time atthe batching site may be relatively short. Therefore the use ofcarbonated mix water and liquid CO₂ may be used to ensure that a desireddose of CO₂ is delivered. For example, in a ready mix operation in whicha carbon dioxide delivery of 1.5% is desired: The volume of gas to beadded is ˜2.66 m³ of gas/m³ of concrete (assuming 350 kg/m³ of cementbeing carbonated at 1.5%). Mix water is typically represented by addedwater and excess moisture contained in the aggregate. If the free mixwater (˜160 L/m³) is carbonated with CO₂ using existing carbonationtechnology, such as that used in the soda industry, to 10 g of CO₂/L ofwater this represents approximately ⅓ of the target carbon dioxidedelivery of 1.5% bwc. Contact with cement results in rapid carbonationof the dissolved CO₂, and the water is quickly ready for additionalcarbon dioxide dissolution once it is in the truck and in contact withthe cement. The use of carbon dioxide in the mix water reduces the totalcarbon dioxide to be added to the truck to 3.66 kg of CO₂ (or about 1.85m³ gas/m³ concrete). This amount may still be too high to be universallydelivered in atmospheric pressure gas form. Therefore liquid CO₂injection into the truck can be used for the balance of the carbondioxide supply. Liquid CO₂ injection of the remaining 3.66 kg CO₂/m³ inthe truck can be done using a controlled flow rate that is based uponsensors and a calibrated CO₂ uptake rate. See Control Mechanisms asdescribed herein. Upon delivery through a nozzle the liquid transformsinto a mixture of solid and gaseous carbon dioxide. The liquid deliverycan result, e.g., in 1.75 kg of solid CO₂ snow (with a density of 1560kg/m³) and 1.9 kg of CO₂ gas (0.96 m³ gas). The gas is immediately beavailable for uptake by the mix water while the solid CO₂ serves as atime delayed CO₂ delivery, as the solid gradually sublimates to gas.This process reduces the gaseous volume injected into the truck toapproximately 29% of the volume needed if the entire CO₂ delivery hadbeen via gaseous CO₂. In some cases part of the concrete mix, e.g., theaggregate, may also be wet. In that case, less mix water is used andcorrespondingly more liquid carbon dioxide. Moisture sensors, e.g., tosense the moisture content of the aggregate, may be used to provideinformation to allow for the adjustment, even on a batch-by-batch basis.This approach can allow for higher uptake rates and greater efficiency.

Exemplary embodiments include a method for producing a cement mix, e.g.,hydraulic cement mix comprising (i) placing components of the cementmix, e.g., hydraulic cement mix in a mixer and mixing the components;and (ii) delivering liquid CO₂ via an opening in a conduit into themixer in such a manner as to cause the liquid CO₂ to form a mixture ofgaseous and solid CO₂ which then contact the cement mix, e.g., hydrauliccement mix. The delivery of the liquid may be controlled in such amanner, e.g., by adjusting flow rate and/or orifice, or other adjustablefeature or measure, as to form a mixture of gaseous to solid carbondioxide in a ratio in the range of 1:10 to 10:1, or 1:5 to 5:1, or 1:3to 3:1, or 1:2 to 2:1, or 1:1.5 to 1.5:1, or 1:1.2 to 1.2 to 1. Thecement mix, e.g., hydraulic cement mix comprises water and the water maybe charged with CO₂ before delivery to the mixer as described herein,for example to a level of at least 2 g CO₂/L water, or at least 4 gCO₂/L water, or at least 6 g CO₂/L water, or at least 8 g CO₂/L water,or at least 9 g CO₂/L water, or at least 10 g CO₂/L water. The mixer maybe any suitable mixer, such as a stationery mixer or a transportablemixer, e.g., the drum of a ready mix concrete truck. When the mixer isthe drum of a ready mix concrete truck, the liquid CO₂ may be suppliedto the mixer at a batching plant, or it may be supplied to the mixerduring transport of the batch to a job site, or even at the job siteitself, or a combination thereof. The method may further includemonitoring a characteristic of the cement mix, e.g., hydraulic cementmix, a gas mixture in contact with the cement mix, e.g., hydrauliccement mix, a component of a cement mix, e.g., hydraulic cement mixapparatus, or a component exposed to the cement mix, e.g., hydrauliccement mix, and modulating the flow of liquid CO₂ according to thecharacteristic monitored. For example, CO₂ concentration, temperature,moisture content, rheology, pH, or a combination thereof may bemonitored, as detailed elsewhere herein. When CO₂ is monitored, it maybe monitored in a portion of gas outside the mixer, e.g. at a leak pointor spill point.

Exemplary embodiments also include a method for producing a cement mix,e.g., hydraulic cement mix comprising (i) contacting components of thecement mix, e.g., hydraulic cement mix with CO₂-charged water, whereinthe water is charged with CO₂ to a level of at least 2 g/L, 3 g/L, 4g/L, 6 g/L, 8 g/L, 9 g/L, or 10 g/L, and mixing the components and thewater. Embodiments further include a method of producing a carbonatedcement mix, e.g., hydraulic cement mix comprising (i) determining a doseof CO₂ to be delivered to the cement mix, e.g., hydraulic cement mix;and (ii) delivering at least 10, 20, 30, 40, 50, 60, 70, 80, 90, or 100%of the dose of CO₂ as CO₂ dissolved in mix water for the cement mix,e.g., hydraulic cement mix. In certain embodiments the dose is 0.1-10%,or 0.5-5%, or 0.5-4%, or 0.5-3%, or 0.5-2%, or 1-5%, or 1-4%, or 1-3%,or 1-2% CO₂ bwc. In certain embodiments the dose is 1.5% CO₂ bwc.Delivery of carbon dioxide-charged mix water as described may becombined in some embodiments with delivery of gaseous and/or liquidcarbon dioxide. Further embodiments in which carbonated mix water isused are described elsewhere herein.

Exemplary embodiments further include an apparatus for carbonating acement mix, e.g., hydraulic cement mix comprising (i) a mixer for mixingthe cement mix, e.g., hydraulic cement mix; (ii) a source of liquid CO₂;and (iii) a conduit operably connecting the source of liquid CO₂ to themixer, wherein the conduit comprises an orifice through which the liquidCO₂ exits the conduit into the mixer. The conduit can include a systemfor regulating the flow of the liquid CO₂ where the system, the orifice,or both, are configured to deliver the liquid CO₂ as a combination ofsolid and gaseous CO₂, such as by regulating flow rate of the liquid CO₂and/or orifice configuration, such as to produce a ratio of solid togaseous CO₂ in the range of 1:10 to 10:1, or 1:5 to 5:1, or 1:3 to 3:1,or 1:2 to 2:1, or 1:1.5 to 1.5:1, or 1:1.2 to 1.2 to 1, for example,between 1:3 and 3:1, or between 1:2 and 2:1. The mixer can be atransportable mixer, such as a drum of a ready-mix truck. The source ofliquid CO₂ and the conduit may remain at a batching facility after thetransportable is charged, or may accompany the transportable mixer whenthe transportable mixer transports the cement mix, e.g., hydrauliccement mix. The apparatus may further include a system for deliveringCO₂-charged water to the mixer comprising a source of CO₂-charged waterand a conduit operably connected to the source and configured to deliverthe water to the mixer, which may in some cases further include acharger for charging the water with CO₂. In certain cases the mixer istransportable and the system for delivering CO₂-charged water to themixer is detachable from the mixer during transport, e.g., if the mixeris the drum of a ready mix truck the system for delivering and,optionally, charging CO₂-charged water remains at the batching facility.

Exemplary embodiments also include an apparatus for producing acarbonated cement mix, e.g., hydraulic cement mix comprising (i) a mixerfor mixing the cement mix, e.g., hydraulic cement mix; and (ii) at leasttwo of (a) a source of gaseous CO₂ operably connected to the mixer andconfigured to deliver gaseous CO₂ to the mixer; (b) a source of liquidCO₂ operably connected to the mixer and configured to deliver liquid CO₂to the mixer and release the liquid CO₂ into the mixer as a mixture ofgaseous and solid CO₂; and (c) a source of carbonated water operablyconnected to the mixer and configured to deliver carbonated water to themixer.

E. Retrofitting Existing Apparatus

In certain embodiments, the methods of the invention include methods andapparatus for retrofitting an existing cement mix, e.g., hydrauliccement mix apparatus to allow for the contact of the mixing cement mix,e.g., hydraulic cement mix with carbon dioxide. As used herein, the term“retrofit” is used in its generally accepted sense to mean installingnew or modified parts or equipment into something previouslymanufactured or constructed. The retrofit may modify the existingapparatus to perform a function for which it was not originally intendedor manufactured. In the case of the present invention, a cement mix,e.g., hydraulic cement mix apparatus to be retrofitted is not originallyconstructed to allow addition of carbon dioxide to a cement mix, e.g.,hydraulic cement mix during mixing of the cement mix, e.g., hydrauliccement mix. Preferably, the retrofitting requires little or nomodification of the existing apparatus. The retrofitting may includedelivering to a site where a pre-existing cement mix, e.g., hydrauliccement mix apparatus is located the components necessary to modify theexisting cement mix, e.g., hydraulic cement mix apparatus to allowexposure of a cement mix, e.g., hydraulic cement mix to carbon dioxideduring mixture. Instructions for one or more procedures in theretrofitting may also be transported or transmitted to the site of theexisting cement mix, e.g., hydraulic cement mix apparatus.

The retrofitting may include installing components necessary to modifythe existing cement mix, e.g., hydraulic cement mix apparatus to allowexposure of a cement mix, e.g., hydraulic cement mix to carbon dioxideduring mixing. The components may include a conduit for delivery ofcarbon dioxide to a cement mix, e.g., hydraulic cement mix mixer. Thecomponents may further include a source of carbon dioxide. In systems inwhich a control system is included, the retrofit may include modifyingthe existing control system of the cement mix, e.g., hydraulic cementmix apparatus to perform functions appropriate to the controlledaddition of carbon dioxide to the cement mix, e.g., hydraulic cementmix. Instructions for such modifications may also be transmitted or sentto the site of the existing cement mix, e.g., hydraulic cement mixapparatus controller. Such modifications can include, for example,modifying the existing controller settings to include timing the openingand closing of a gas supply valve to deliver a flow of carbon dioxide ata predetermined flow rate for a predetermined time from the carbondioxide source via the conduit to the mixer at a certain stage in thehydraulic mix apparatus operations. They may also include modifying thecontroller to modify the timing and/or amount of water addition to thecement mix, e.g., hydraulic cement mix, addition of admixture, and anyother suitable parameter. Alternatively, or in addition to, modifyingthe existing controller, the retrofitting may include providing one ormore new controllers to the pre-existing cement mix, e.g., hydrauliccement mix apparatus. The retrofitting can include transporting the newcontroller or controllers to the site of the existing cement mix, e.g.,hydraulic cement mix apparatus. In addition, one or more sensors, suchas sensors for sensing the positions and/or states of one or morecomponents of the existing cement mix, e.g., hydraulic cement mixapparatus, which were not part of the original manufactured equipment,may be installed. The retrofit may include transporting one or moresensors to the site of the existing cement mix, e.g., hydraulic cementmix apparatus. Actuators, which may be actuators in the retrofittedapparatus, e.g., a gas supply valve, or in the original equipment, e.g.,to move or start or stop various operations such as addition of water,may be operably connected to the retrofitted controller in order tomodify the operations of the cement mix, e.g., hydraulic cement mixapparatus according to the requirements of contacting the cement mix,e.g., hydraulic cement mix with carbon dioxide. The retrofit may includetransporting one or more sensors to the site of the existing cement mix,e.g., hydraulic cement mix apparatus.

III. Methods

In certain embodiments, the invention provides methods for producing acarbonated cement mix in a mix operation in a cement mix apparatuscomprising (i) contacting a cement mix comprising cement binder andaggregate in a mixer with carbon dioxide while the cement mix is mixing;(ii) monitoring a characteristic of the cement binder, the cement mix, agas mixture in contact with the cement mix or the mixer, or a componentof the cement mix apparatus; and (iii) modulating the exposure of thecement mix to the carbon dioxide or another characteristic of the cementmix operation, or a combination thereof according to the characteristicmonitored in step (ii). In some cases, only exposure of the cement mixto the carbon dioxide is modulated; in other cases, only anothercharacteristic of the cement mix operation is modulated; and in othercases, both are modulated.

The cement binder may be any suitable cement binder as described herein,i.e., a cement binder containing calcium species capable of reactingwith carbon dioxide to form stable or metastable reaction products, suchas carbonates. The cement binder may be a hydraulic cement, for example,a Portland cement. “Cement mix,” as that term is used herein, includes amix of a cement binder, e.g., a hydraulic cement, such as a Portlandcement, with aggregate; “concrete” is generally synonymous with “cementmix” as those terms are used herein.

The mix operation may be any operation in which a cement mix/concrete isproduced for any of the various uses of such a mix. Thus, the cement mixoperation may be an operation in a mixer at a precast facility forproducing a cement mix for use in a dry cast or wet cast operation. Inother embodiments, the cement mix operation may be an operation in amixer for a ready mix operation, e.g., the drum of a ready mix truck.Any other suitable cement mix operation may also be used, so long as itis amenable to addition of carbon dioxide to the cement mix duringmixing, for example, a mixer on site at a construction site. Thus,additional examples include pug mill or twin shaft continuous mixersthat can be used for roller compacted concrete (dry mix) or CTB (cementtreated base) for road stabilization, which are continuous mixapplications rather than batch. While some of the aspects of waterproportioning might not be achievable there still exists the possibilityto add CO₂ during the mixing step.

The characteristic monitored may be any suitable characteristic thatprovides useful feedback to inform modulation of exposure of the cementmix to carbon dioxide or another characteristic of the cement mixoperation. In certain embodiments, the characteristic monitored is (a)mass of cement binder added to the cement mix, (b) location of thecement binder in the mix apparatus (e.g., coordinating carbon dioxidedelivery with delivery of cement binder; may be achieved by sensing thelocation of the cement mix or by timing of the mix sequence, which canbe input to the controller), (c) carbon dioxide content of a gas mixturewithin the mixer in contact with the cement mix, (d) carbon dioxidecontent of a gas mixture exiting from the mixer, (e) carbon dioxidecontent of gas mixture in the vicinity of the mix apparatus, (f)temperature of the cement mix or a component of the mix apparatus incontact with the cement mix, (g) rheology of the cement mix, (h)moisture content of the cement mix, or (i) pH of the cement mix. Thelocation of water in the mix apparatus also be monitored, e.g., todetermine when water addition is complete. These characteristics andmethods and apparatus for monitoring them are as described elsewhereherein. When the mass of the cement binder is monitored, the totalamount of carbon dioxide to be added to the cement mix may be modulatedto accord with a predetermined desired exposure, e.g., if a 1.5% carbondioxide/cement exposure is desired, the exact mass used in a particularbatch may be used to determine the exact total carbon dioxide to beadded to the batch (which may be used as is, or modified in response toother characteristics that are monitored). When location of the cementbinder or water in the mix apparatus is monitored, the modulation ofcarbon dioxide flow may be a simple on/off, e.g., when the cement mixand/or water is determined to have entered the mixer, carbon dioxideflow may be turned on at that time or at a predetermined time after thattime. In certain embodiments, the characteristic monitored in step (ii)comprises carbon dioxide content of a gas mixture exiting from themixer, e.g., at a leak point of the mixer. In this embodiment, and/or inother embodiments in which a carbon dioxide content of a gas mixture ismonitored, the exposure of the cement mix to carbon dioxide can bemodulated when the carbon dioxide content of the gas mixture reaches athreshold value, and/or when the rate of change of the carbon dioxidecontent of the gas mixture reaches a threshold value. The modulation canbe an increase in the rate of carbon dioxide addition to the cement mix,a decrease, or even a full stop. In certain embodiments, thecharacteristic monitored is the temperature of the cement mix or acomponent of the mix apparatus in contact with the cement mix. Forexample, a wall of the mixer may be monitored for temperature. Theexposure of the cement mix to carbon dioxide can be modulated when thetemperature of the cement mix or a component of the mix apparatus incontact with the cement mix, or a combination of a plurality of suchtemperatures, reaches a threshold value and/or when the rate of changeof the temperature of the cement mix or a component of the mix apparatusin contact with the cement mix reaches a threshold value. If temperatureis used as a measure for the threshold value, it may be an absolutetemperature, or it may be a temperature relative to the temperature ofthe mix before the addition of carbon dioxide, e.g., a temperature thatis a certain number of degrees above the starting temperature, forexample 10-50° C. above the starting value, or 10-40° C. above thestarting value, or 10-30° C. above the starting value. The exactdifference between starting and threshold temperature may bepredetermined for a particular mix recipe by determining therelationship between carbonation and temperature for that recipe, or forthat particular cement binder in relation to other components of thatrecipe.

In certain embodiments, a plurality of characteristics of the cementbinder, the cement mix, a gas mixture in contact with the cement mix orthe mixer, or a component of the cement mix apparatus are monitored,e.g., at least 2, 3, 4, 5, 6, 7, 8, 9, or 10 characteristics, forexample, at least 2 characteristics. In certain embodiments, at least 2of (a) mass of cement binder added to the cement mix, (b) location ofthe cement binder in the mix apparatus, (c) carbon dioxide content of agas mixture within the mixer in contact with the cement mix, (d) carbondioxide content of a gas mixture exiting from the mixer, (e) carbondioxide content of gas mixture in the vicinity of the mix apparatus, (f)temperature of the cement mix or a component of the mix apparatus incontact with the cement mix, (g) rheology of the cement mix, (h)moisture content of the cement mix, or (i) pH of the cement mix aremonitored. In certain embodiments, at least 3 of (a) mass of cementbinder added to the cement mix, (b) location of the cement binder in themix apparatus, (c) carbon dioxide content of a gas mixture within themixer in contact with the cement mix, (d) carbon dioxide content of agas mixture exiting from the mixer, (e) carbon dioxide content of gasmixture in the vicinity of the mix apparatus, (f) temperature of thecement mix or a component of the mix apparatus in contact with thecement mix, (g) rheology of the cement mix, (h) moisture content of thecement mix, or (i) pH of the cement mix are monitored. In certainembodiments, at least 4 of (a) mass of cement binder added to the cementmix, (b) location of the cement binder in the mix apparatus, (c) carbondioxide content of a gas mixture within the mixer in contact with thecement mix, (d) carbon dioxide content of a gas mixture exiting from themixer, (e) carbon dioxide content of gas mixture in the vicinity of themix apparatus, (f) temperature of the cement mix or a component of themix apparatus in contact with the cement mix, (g) rheology of the cementmix, (h) moisture content of the cement mix, or (i) pH of the cement mixare monitored. In certain embodiments, at least 5 of (a) mass of cementbinder added to the cement mix, (b) location of the cement binder in themix apparatus, (c) carbon dioxide content of a gas mixture within themixer in contact with the cement mix, (d) carbon dioxide content of agas mixture exiting from the mixer, (e) carbon dioxide content of gasmixture in the vicinity of the mix apparatus, (f) temperature of thecement mix or a component of the mix apparatus in contact with thecement mix, (g) rheology of the cement mix, (h) moisture content of thecement mix, or (i) pH of the cement mix are monitored. In certainembodiments, at least 6 of (a) mass of cement binder added to the cementmix, (b) location of the cement binder in the mix apparatus, (c) carbondioxide content of a gas mixture within the mixer in contact with thecement mix, (d) carbon dioxide content of a gas mixture exiting from themixer, (e) carbon dioxide content of gas mixture in the vicinity of themix apparatus, (f) temperature of the cement mix or a component of themix apparatus in contact with the cement mix, (g) rheology of the cementmix, (h) moisture content of the cement mix, or (i) pH of the cement mixare monitored.

In certain embodiments, the method alternatively, or additionally,include monitoring the time of exposure of the cement mix to the carbondioxide, the flow rate of the carbon dioxide, or both.

When an additional characteristic of the mix operation is modulated inresponse to the monitoring, it may be any suitable characteristic. Incertain embodiments, the additional characteristic includes (a) whetheror not an admixture is added to the cement mix, (b) type of admixtureadded to the cement mix, (c) timing of addition of admixture to thecement mix, (d) amount of admixture added to the cement mix, (e) amountof water added to the cement mix, (f) timing of addition of water to thecement mix, (g) cooling of the cement mix during or after carbon dioxideaddition, or a combination thereof. If an admixture is used, it may beany suitable admixture for adjusting a characteristic of the cement mix,e.g., an admixture to adjust the rheology (flowability) of the mix, forexample, in a wet cast operation. Examples of suitable admixtures aredescribed herein, e.g., carbohydrates or carbohydrate derivatives, suchas sodium gluconate.

The characteristic may be monitored, such as by one or more sensors.Such sensors may transmit information regarding the characteristic to acontroller which processes the information and determines if amodulation of carbon dioxide exposure or another characteristic of themix operation is required and, if so, transmits a signal to one or moreactuators to carry out the modulation of carbon dioxide exposure orother characteristic of the mix operation. The controller may be at thesite of the mix operation or it may be remote. Such sensors,controllers, and actuators are described further elsewhere herein. If acontroller is used, it may store and process the information obtainedregarding the characteristic monitored in step (ii) for a first batch ofcement mix and adjust conditions for a subsequent second cement mixbatch based on the processing. For example, the controller may adjustthe second mix recipe, e.g., amount of water used or timing of wateraddition, or carbon dioxide exposure in the second batch to improvecarbon dioxide uptake, or to improve rheology or other characteristicsof the mix, e.g., by addition and/or amount of an admixture, and/ortiming of addition of the admixture. In such embodiments in which one ormore conditions of a second mix operation are adjusted, in certainembodiments the one or more conditions of the second mix operationincludes (a) total amount of carbon dioxide added to the cement mix, (b)rate of addition of carbon dioxide, (c) time of addition of carbondioxide to the cement mix, (d) whether or not an admixture is added tothe cement mix, (e) type of admixture added to the cement mix, (f)timing of addition of admixture to the cement mix, (g) amount ofadmixture added to the cement mix, (h) amount of water added to thecement mix, (i) timing of addition of water to the cement mix, (j)cooling the cement mix during or after carbon dioxide addition, or acombination thereof. The controller can also receive additionalinformation regarding one or more characteristics of the cement mixmeasured after the cement mix leaves the mixer, and adjusts conditionsfor the second cement mix batch based on processing that furthercomprises the additional information. In certain embodiments, the one ormore characteristics of the cement mix measured after the cement mixleaves the mixer comprises (a) rheology of the cement mix at one or moretime points, (b) strength of the cement mix at one or more time points,(c) shrinkage of the cement mix, (d) water absorption of the cement mix,or a combination thereof. Other characteristics include elastic modulus,density, and permeability. Any other suitable characteristic may bemeasured. The characteristic monitored can depend on the requirementsfor a particular mix batch, although other characteristics may also bemonitored to provide data to the controller for future batches in whichthose characteristics would be required.

In embodiments in which a controller adjusts conditions for a second mixoperation based on input from a first mix operation, the second mixoperation may be in the same mix facility or it may be in a differentmix facility. In certain embodiments, the controller, one or moresensors, one or more actuators, or combination thereof, transmitsinformation regarding the characteristics monitored and conditionsmodulated to a central controller that receives information from aplurality of controllers, sensors, actuators, or combination thereof,each of which transmits information from a separate mixer to the centralcontroller. Thus, for example, a first mix facility may have a firstsensor to monitor a first characteristic of the first mix operation, anda second mix facility may have a second sensor to monitor a secondcharacteristic of a second mix operation, and both may send informationregarding the first and second characteristics to a central controller,which processes the information and transmit a signal to the first,second, or even a third mix operation to adjust conditions based on thefirst and second signals from the first and second sensors. Additionalinformation that will be typically transmitted to the central controllerincludes mix components for the mixes at the first and second mixoperations (e.g., type and amount of cement binder, amount of water andw/c ratio, types and amounts of aggregate, whether aggregate was wet ordry, admixtures, and the like) amount, rate, and timing of carbondioxide addition, and any other characteristic of the first and secondmix operations that would be useful for determining conditions tomodulate future mix operations based on the characteristics achieved inpast mix operations. Any number of mix operations may input informationto the central controller, e.g., at least 2, 3, 4, 5, 6, 7, 8, 9, or 10mix operations, or at least 15, 20, 25, 30, 40, 50, 60, 70, 80, 90, or100 mix operations. The central controller may also receive any otherinformation that may be suitable to informing decisions regarding mixoperations to optimize one or more conditions of the mix operationand/or of the cement mix produced in the operation. For example, thecentral controller may receive information from experiments conductedwith various types of cements (e.g., various types of Portland cements)carbonated under various conditions, and/or exposed to variousadmixtures, such as at different times, or in different concentrations,and the like, and the resulting characteristics of the cement mix, suchas rheology at one or more time points, strength at one or more timepoints, and the like. Any other suitable information, such asinformation published in literature, or obtained in any manner, may beinput into the central controller. The information the centralcontroller receives can be processed and used to adjust cement mixoperations at any mix operation to which the central controller cantransmit outputs. Thus, the central controller can learn from numerousmix operations to optimize future operations and, over time, canaccumulate a database to inform decisions in mix operations at a mixsite even if a particular mix recipe and/or conditions have never beenused at that site. The central controller can match to past mix recipes,or predict optimum conditions for a new mix recipe based on suitablealgorithms using information in its database, or both.

In certain embodiments, the invention provides a method of carbonating acement mix in a mixer that is not completely airtight in such a way asto achieve an efficiency of carbonation of at least 60, 70, 80, 90, 95,96, 97, 98, or 99%, wherein efficiency of carbonation is the amount ofcarbon dioxide retained in the cement mix per the total amount of carbondioxide to which the cement mix is exposed during mixing. The mixer mayhave leak points and other aspects that make it less than airtight, suchas seen in a typical mixer for a precast operation. The mixer may be,e.g., the drum of a ready mix truck which has a large opening to theoutside atmosphere. Such efficiency may be achieved, e.g., by using anyof the methods to modulate the exposure of the cement mix to carbondioxide as detailed above.

In certain embodiments, the invention provides a method for producing acement mix, e.g., hydraulic cement mix comprising (i) contacting acement mix, e.g., hydraulic cement mix comprising a first portion ofwater and hydraulic cement in a mixer with carbon dioxide while thecement mix, e.g., hydraulic cement mix is mixing; and (ii) adding asecond portion of water to the cement mix, e.g., hydraulic cement mix.In some aspects of this embodiment, the contacting comprises directing aflow of carbon dioxide to the cement mix, e.g., hydraulic cement mix.The second portion of water may be added to the cement mix, e.g.,hydraulic cement mix during said flow or after said flow has ceased, forexample, after said flow has ceased. The method may include addingaggregate to the cement mix, e.g., hydraulic cement mix to produce aconcrete mix; in certain embodiments, the aggregate comprises some orall of the first portion of water. The aggregate may be added before thecontacting with the carbon dioxide. In certain embodiments, the methodincludes (iii) adding an admixture to the cement mix, e.g., hydrauliccement mix, such as an admixture that modulates the flowability of thecement mix, e.g., hydraulic cement mix. In embodiments in which anadmixture to modulate flowability is added, the admixture may added inan amount to achieve a flowability in a predetermined range offlowabilities, such as a predetermined range of flowabilities that isdetermined by allowing for a margin from the flowability of the cementmix, e.g., hydraulic cement mixture without the addition of carbondioxide. The admixture may be selected from the group consisting of apolycarboxylate superplasticer, a naphthalene HRWR, or any combinationthereof. In certain embodiments, the admixture contains sodiumgluconate, sucrose, glucose, molasses, corn syrup, EDTA, or acombination thereof. In certain embodiments, the admixture containssodium gluconate. In certain embodiments, the admixture containssucrose. In certain embodiments, the admixture contains glucose. Incertain embodiments, the admixture contains molasses. In certainembodiments, the admixture contains corn syrup. In certain embodiments,the admixture contains EDTA. In certain embodiments, the cement mix,e.g., hydraulic cement mix comprises Portland cement. Whether or not thecement mix, e.g., hydraulic cement mix comprises Portland cement, incertain embodiments cement mix, e.g., hydraulic cement mix comprisingthe first portion of water comprises an amount of water so that theratio of water to cement (w/c ratio) is equal to or less than 0.5. Incertain of these embodiments, the first portion of water comprises anamount of water so that the w/c ratio is in the range 0.1 to 0.5. thecarbon dioxide to which the cement mix, e.g., hydraulic cement mix isexposed may be at least 50% pure. The cement mix, e.g., hydraulic cementmix may be contacted with carbon dioxide by flowing carbon dioxide overthe surface of the mixing cement mix, e.g., hydraulic cement mix. Theflow of carbon dioxide directed to the cement mix, e.g., hydrauliccement mix, e.g., the surface of the mix, may last for 5 minutes orless, for example, the flow of carbon dioxide directed to the cementmix, e.g., hydraulic cement mix may last for 0.5-5 minutes. In certainembodiments, in which solid carbon dioxide is introduced into the cementmix, the solid carbon dioxide sublimates to gaseous carbon dioxide andthe delivery may be extended to more than 20, 30, 40, 50, or 60 minutes.The method may further comprise monitoring a characteristic of thecement mix, e.g., hydraulic cement mix, a gas mixture in contact withthe cement mix, e.g., hydraulic cement mix, a component of a cement mix,e.g., hydraulic cement mix apparatus, or a component exposed to thecement mix, e.g., hydraulic cement mix, and modulating the flow ofcarbon dioxide according to the characteristic monitored. For example,the method may further comprise monitoring a carbon dioxideconcentration in a portion of gas adjacent to the cement mix, e.g.,hydraulic cement mix, such as in a portion of gas in the mixer, or in aportion of gas outside the mixer, or both. The carbon dioxideconcentration may be monitored by a sensor. The sensor may transmit asignal to a controller. The controller may process the signal andtransmits a signal to an actuator according to the results of theprocessing, such as a controllable valve for controlling the flow ofcarbon dioxide to contact the cement mix, e.g., hydraulic cement mix. Inaddition to, or instead of carbon dioxide, a temperature of the cementmix, e.g., hydraulic cement mix, the mixer, or of another componentexposed to the cement mix, e.g., hydraulic cement mix may be monitored,for example, the temperature of the mixer may be monitored, or thetemperature of the cement mix, e.g., hydraulic cement mix inside themixer may be monitored, or the temperature of a portion of the cementmix, e.g., hydraulic cement mix that is transported outside the mixermay be monitored. The contacting of the cement mix, e.g., hydrauliccement mix with carbon dioxide may be modulated according to thetemperature monitored, for example, when the temperature beingmonitored, or a combination of temperatures being monitored, exceeds athreshold value. The threshold value may be a value determined relativeto the initial temperature of the cement mix, e.g., hydraulic cement mixbefore addition of carbon dioxide, such as a threshold temperature orrange of temperatures relative to the initial temperature as describedherein. Alternatively, the threshold value may be an absolute value. Thetemperature may be monitored by a sensor. The sensor may transmit asignal to a controller. The controller may process the signal andtransmit a signal to an actuator according to the results of theprocessing. The actuator may comprise a controllable valve forcontrolling the flow of carbon dioxide to contact the cement mix, e.g.,hydraulic cement mix. The method of contacting the hydraulic cement withcarbon dioxide may include, in any of these embodiments, controlling thecontacting of the cement mix, e.g., hydraulic cement mix with the carbondioxide is controlled to achieve a desired level of carbonation, such asa level as described herein, for example, at least 0.5, 1, 2, 3, or 4%.In certain embodiments, the exposure of the cement mix to carbon dioxideis modulated so as to provide an efficiency of carbon dioxide uptake ofat least 60, 70, 80, 90, 95, 96, 97, 98, or 99%, for example, at least70%.

In certain embodiments, the invention provides a method for producing acement mix, e.g., hydraulic cement mix comprising (i) contacting acement mix, e.g., hydraulic cement mix comprising water and hydrauliccement in a mixer with carbon dioxide while the cement mix, e.g.,hydraulic cement mix is mixing, wherein the carbon dioxide is contactedwith the surface of the cement mix, e.g., hydraulic cement mix bydirecting a flow of carbon dioxide to the surface of the mix fromoutside the mix, and wherein the flow lasts less than 5 min. In certainembodiments, the cement mix, e.g., hydraulic cement mix comprisesaggregate. The cement mix, e.g., hydraulic cement mix may furthercomprise an admixture. In certain embodiments, the mixer is atransportable mixer, such as a drum of a ready-mix truck. In certainembodiments, the mixer is a mixer for pre-cast concrete. The method mayfurther comprise controlling the flow of the carbon dioxide according tofeedback from one or more sensors that monitor a characteristic selectedfrom the group consisting of a characteristic of the cement mix, e.g.,hydraulic cement mix, a gas mixture in contact with the cement mix,e.g., hydraulic cement mix, a component of a cement mix, e.g., hydrauliccement mix apparatus, or a component exposed to the cement mix, e.g.,hydraulic cement mix.

In certain embodiments, the invention provides a method for producing ahydraulic cement mix comprising (i) contacting a cement mix, e.g.,hydraulic cement mix comprising water and hydraulic cement in a mixerwith carbon dioxide while the cement mix, e.g., hydraulic cement mix ismixing, wherein the carbon dioxide is contacted with the surface of thecement mix, e.g., hydraulic cement mix by directing a flow of carbondioxide to the surface of the mix from outside the mix, and wherein thecarbon dioxide is a component of a gaseous mixture that comprises atleast 10, 20, 30, 40, 50, 60, 70, 80, 90, 95, or 99% carbon dioxide,such as at least 50% carbon dioxide. In certain embodiments, thehydraulic cement comprises aggregate. In certain embodiments, thehydraulic cement comprises an admixture. In certain embodiments, themixer is a transportable mixer, such as a drum of a ready-mix truck. Incertain embodiments, the mixer is a mixer for pre-cast concrete.

In certain embodiments, the invention provides a method for producing acement mix, e.g., hydraulic cement mix comprising (i) contacting acement mix, e.g., hydraulic cement mix in a mixer with carbon dioxidewhile the cement mix, e.g., hydraulic cement mix is mixing; and (ii)adding an admixture to the cement mix, e.g., hydraulic cement mix. Thecontacting may be achieved by directing a flow of carbon dioxide to thecement mix, e.g., hydraulic cement mix. In certain embodiments, theadmixture is an admixture that modulates the flowability of the cementmix, e.g., hydraulic cement mix. In certain of these embodiments, theadmixture may be added in an amount to achieve a flowability in apredetermined range of flowabilities, such as a predetermined range offlowabilities determined by allowing for a margin from the flowabilityof the cement mix, e.g., hydraulic cement mixture without the additionof carbon dioxide, for example, as described elsewhere herein. Incertain aspects of the fourth embodiment, the admixture is selected fromthe group consisting of a polycarboxylate superplasticer, a naphthaleneHRWR, or any combination thereof.

In certain embodiments, the invention provides a method for producing acement mix, e.g., hydraulic cement mix comprising (i) contacting acement mix, e.g., hydraulic cement mix in a mixer with carbon dioxidewhile the cement mix, e.g., hydraulic cement mix is mixing, wherein thecarbon dioxide is exposed to the cement mix, e.g., hydraulic cement mixwhen the w/c ratio of the cement mix, e.g., hydraulic cement mix is lessthan or equal to 0.4. In certain embodiments, the contacting is achievedby directing a flow of carbon dioxide to the cement mix, e.g., hydrauliccement mix. In certain aspects of this embodiment, the w/c ratio of thecement mix, e.g., hydraulic cement mix is 0.05-0.4. The method mayfurther comprise monitoring a characteristic of the cement mix, e.g.,hydraulic cement mix, a gas mixture in contact with the cement mix,e.g., hydraulic cement mix, a component of a cement mix, e.g., hydrauliccement mix apparatus, or a component exposed to the cement mix, e.g.,hydraulic cement mix, and modulating the flow of carbon dioxideaccording to the characteristic monitored. The method may comprise (ii)adding an admixture to the cement mix, e.g., hydraulic cement mix, suchas an admixture that modulates the flowability of the cement mix, e.g.,hydraulic cement mix, for example an admixture to modulate flowabilityof type and/or amount as described elsewhere herein.

In certain embodiments, the invention provides a method for producing acement mix, e.g., hydraulic cement mix comprising (i) contacting acement mix, e.g., hydraulic cement mix in a mixer with carbon dioxidewhile the cement mix, e.g., hydraulic cement mix is mixing at a firstlocation, and (ii) transporting the cement mix, e.g., hydraulic cementmix to a second location where the cement mix, e.g., hydraulic cementmix is used. In certain aspects of this embodiment, said contacting isachieved by directing a flow of carbon dioxide to the cement mix, e.g.,hydraulic cement mix. The second location may be at least 0.1 mile fromthe first location. The second location may be at least 0.5 mile fromthe first location. The method may comprise monitoring a characteristicof the cement mix, e.g., hydraulic cement mix, a gas mixture in contactwith the cement mix, e.g., hydraulic cement mix, a component of a cementmix, e.g., hydraulic cement mix apparatus, or a component exposed to thecement mix, e.g., hydraulic cement mix, and modulating the flow ofcarbon dioxide according to the characteristic monitored. The method maycomprise (ii) adding an admixture to the cement mix, e.g., hydrauliccement mix, such as an admixture that modulates the flowability of thecement mix, e.g., hydraulic cement mix.

In certain embodiments, the invention provides a method for producing acement mix, e.g., hydraulic cement mix comprising (i) contacting acement mix, e.g., hydraulic cement mix in a mixer with carbon dioxidewhile the cement mix, e.g., hydraulic cement mix is mixing with a flowof carbon dioxide directed to the cement mix, e.g., hydraulic cementmix, (ii) monitoring a characteristic of the cement mix, e.g., hydrauliccement mix, a gas mixture in contact with the cement mix, e.g.,hydraulic cement mix, a component of a cement mix, e.g., hydrauliccement mix apparatus, or a component exposed to the cement mix, e.g.,hydraulic cement mix; and (iii) modulating the exposure of the cementmix, e.g., hydraulic cement mix to the carbon dioxide according to thecharacteristic monitored in step (ii). The method may comprisemonitoring a carbon dioxide concentration in a portion of gas adjacentto the cement mix, e.g., hydraulic cement mix, e.g., a portion of gas inthe mixer, or a portion of gas outside the mixer. The carbon dioxideconcentration may be monitored by a sensor. The sensor may transmit asignal to a controller. The controller may process the signal andtransmit a signal to an actuator according to the results of theprocessing, for example, an actuator comprising a valve for controllingthe flow of carbon dioxide to contact the cement mix, e.g., hydrauliccement mix. The method may comprise monitoring a temperature of thecement mix, e.g., hydraulic cement mix, the mixer, or of anothercomponent exposed to the cement mix, e.g., hydraulic cement mix ismonitored. A temperature of the mixer may be monitored, or a temperatureof the cement mix, e.g., hydraulic cement mix inside the mixer may bemonitored, or a temperature of a portion of the cement mix, e.g.,hydraulic cement mix that is transported outside the mixer may bemonitored, or any combination thereof. The contacting of the cement mix,e.g., hydraulic cement mix with carbon dioxide may be modulatedaccording to the temperature monitored. The contacting of the cementmix, e.g., hydraulic cement mix with the carbon dioxide may be modulatedwhen the temperature being monitored, or a combination of temperaturesbeing monitored, exceeds a threshold value, such as a value determinedrelative to the initial temperature of the cement mix, e.g., hydrauliccement mix before addition of carbon dioxide, such as a threshold valueas described elsewhere herein. Alternatively, the threshold value may bean absolute value. The temperature may be monitored by a sensor. Thesensor may transmit a signal to a controller. The controller may processthe signal and transmit a signal to an actuator according to the resultsof the processing. The actuator may comprise a controllable valve forcontrolling the flow of carbon dioxide to contact the cement mix, e.g.,hydraulic cement mix.

In certain embodiments, the invention provides a method for producing acement mix, e.g., hydraulic cement mix comprising (i) contacting a firstportion of cement mix, e.g., hydraulic cement mix comprising a firstportion of water and hydraulic cement in a mixer while the cement mix,e.g., hydraulic cement mix is mixing; and (ii) adding a second portionof cement mix, e.g., hydraulic cement mix to the first portion. Incertain aspects of this embodiment, said contacting is achieved bydirecting a flow of carbon dioxide to the first portion of cement mix,e.g., hydraulic cement mix.

In certain embodiments, the invention provides a method of retrofittingan existing cement mix, e.g., hydraulic cement mixing apparatuscomprising a mixer, comprising operably connecting to the existingcement mix, e.g., hydraulic cement mixing apparatus a system forcontacting a cement mix, e.g., hydraulic cement mix within the mixerwith carbon dioxide during mixing of the cement mix, e.g., hydrauliccement mix. In certain aspects of this embodiment, the system to contactthe cement mix, e.g., hydraulic cement mix in the mixer with carbondioxide comprises a system to direct a flow of carbon dioxide to thecement mix, e.g., hydraulic cement mix during mixing of the cement mix,e.g., hydraulic cement mix. The method may also comprise operablyconnecting a source of carbon dioxide to a conduit for delivering thecarbon dioxide to the mixer. The method may also comprise operablyconnecting the conduit to the mixer. The system may comprise an actuatorfor modulating delivery of carbon dioxide from the source of carbondioxide through the conduit. The system may comprise a control systemfor controlling the actuator, operably connected to the actuator. Thecontrol system may comprises a timer and a transmitter for sending asignal to the actuator based on the timing of the timer. The method maycomprise connecting the actuator to an existing control system for thecement mix, e.g., hydraulic cement mixing apparatus. The method maycomprise modifying the existing control system to control the actuator.The actuator may be operably connected to or configured to be operablyconnected to the conduit, the mixer, a control system for the mixer, orto a source of carbon dioxide, or a combination thereof. The actuatormay control a valve so as to control delivery of carbon dioxide to themixer. The method may comprise adding to the existing cement mix, e.g.,hydraulic cement mixing apparatus one or more sensors operably connectedto, or configured to be operably connected to, a control system, formonitoring one or more characteristics of the cement mix, e.g.,hydraulic cement mix, a gas mixture in contact with the cement mix,e.g., hydraulic cement mix, a component of the cement mix, e.g.,hydraulic cement mixing apparatus, or a component exposed to the cementmix, e.g., hydraulic cement mix, for example, one or more sensors is asensor for monitoring carbon dioxide concentration of a gas or atemperature.

IV. Apparatus and Systems

In one aspect, the invention provides apparatus and systems. Theapparatus may include one or more of a conduit for supplying carbondioxide from a carbon dioxide source to a mixer, a source of carbondioxide, a mixer, one or more sensors, one or more controllers, one ormore actuators, all as described herein.

For example, in certain embodiments the invention provides an apparatusfor addition of carbon dioxide to a mixture comprising hydraulic cement,where the apparatus comprises a mixer for mixing the cement mix, e.g.,hydraulic cement mix, and a system for delivering carbon dioxide to thecement mix, e.g., hydraulic cement mix in the mixer during mixing. Incertain embodiments, the system for delivering carbon dioxide isconfigured to deliver carbon dioxide to the surface of the cement mix,e.g., hydraulic cement mix during mixing. The system may include acarbon dioxide source, a conduit operably connecting the source and themixer for delivery of carbon dioxide to the mixer, a metering system formetering flow of carbon dioxide in the conduit, and an adjustable valveto adjust the flow rate. In addition, the apparatus may include one ormore sensors to sense carbon dioxide content of gas in the mixer, oroutside the mixer. The apparatus may also include one or more sensorsfor sensing the temperature of the cement mix, e.g., hydraulic cementmix, or the mixer or other component. The apparatus may further includea controller that is operably connected to the one or more sensors,e.g., to one or more temperature sensors, one or more carbon dioxidesensors, or a combination thereof, and which is configured to receivedata from the one or more sensors. The controller may be configured todisplay the data, e.g., so that a human operator may adjust flow orother parameters based on the data. The controller may be configured toperform one or more operations on the data, and to send output to one ormore actuators based on the results of the one or more operations. Forexample, the controller may be configured to send output to a anadjustable valve causing it to modulate the flow of carbon dioxide inthe conduit, e.g., to stop the flow after a particular temperature, orcarbon dioxide concentration, or both, has been achieved.

In certain embodiments the invention provides a system for retrofittingan existing cement mix, e.g., hydraulic cement mix apparatus to allowcarbon dioxide to be contacted with a cement mix, e.g., hydraulic cementmix during mixing. The system may be configured to be transported from asite remote from the site of the existing cement mix, e.g., hydrauliccement mix apparatus to the site of the existing cement mix, e.g.,hydraulic cement mix apparatus.

In certain embodiments the invention provides an apparatus forcarbonating a cement mix comprising a cement binder and aggregate in acement mix apparatus during a mix operation, comprising (i) a mixer formixing the cement mix; (ii) a system for contacting the cement mix inthe mixer with carbon dioxide operably connected to the mixer andcomprising an actuator for modulating a flow of carbon dioxide to themixer; (iii) a sensor positioned and configured to monitor acharacteristic of the mix operation; and to transmit informationregarding the characteristic to a controller; (iv) the controller,wherein the controller is configured (e.g., programmed) to process theinformation and determine whether or not and/or to what degree tomodulate the flow of carbon dioxide to the mixer and to transmit asignal to the actuator to modulate the flow of carbon dioxide to themixer. In addition to, or instead of, the actuator for modulating a flowof carbon dioxide, the system may include one or more actuators formodulating another characteristic of the system, and the controller maybe configured to determine whether or not and to what degree to modulatethe other characteristic, and transmit a signal to the actuator formodulating the other characteristic.

The mixer may be any suitable mixer so long as it can be configured withthe remaining elements of the apparatus, such as mixers describedherein. In certain embodiments, the mixer is a stationery mixer, such asa mixer used in a precast operation. In certain embodiments, the mixeris a transportable mixer, such as the drum of a ready mix truck. Inembodiments in which the mixer is transportable, one or more of theelements of the control system for contacting the cement mix with carbondioxide, sensing a characteristic, controlling one or morecharacteristics such as carbon dioxide flow, and actuators, may beconfigured to be transported along with the mixer, or may be configuredto be detachable from the mixer, for example, to remain at a batchingstation for a ready mix truck. See, e.g. FIGS. 3 and 4, which showelements of the carbon dioxide delivery system in eithernon-transportable or transportable form. Elements of the control systemmay be similarly transportable or non-transportable. It will beappreciated that some parts of the system may be transported whileothers remain at, e.g. the batching station. For example, all carbondioxide may be delivered at the batching station but certaincharacteristics of the cement mix, e.g., rheology, may be monitoredwhile the truck in en route to the job site, and, if necessary, thecement mix may be modulated based on the monitoring, e.g., by additionof an admixture, or water, etc.

The system for contacting the cement mix in the mixer with carbondioxide may be any suitable system, such as the systems describedherein. In certain embodiments, the system is configured to delivergaseous carbon dioxide to the cement mix. In certain embodiments, thesystem is configured to deliver liquid carbon dioxide to the cement mixin such a manner that the liquid carbon dioxide is converted to gaseousand solid carbon dioxide as it is delivered to the cement mix, asdescribed herein. The system may be configured to deliver carbon dioxideto the surface of the mixing cement mix, or underneath the surface, or acombination thereof. In the case of a ready mix truck, the system forcontacting the cement in the mixer with carbon dioxide may share aconduit with the water delivery system, by a T junction in the conduit,such that either water or carbon dioxide can be delivered to a finalcommon conduit. See Examples 2 and 6.

The sensor may be any suitable sensor so long as it is configured andpositioned to transmit relevant information to the controller. Incertain embodiments, the characteristic of the mix operation that ismonitored by the sensor comprises a characteristic of the cement binder,the cement mix, a gas mixture in contact with the cement mix or themixer, or a component of the cement mix apparatus. In certainembodiments, the sensor is configured and positioned to monitor (a) massof cement binder added to the cement mix, (b) location of the cementbinder in the mix apparatus, (c) carbon dioxide content of a gas mixturewithin the mixer in contact with the cement mix, (d) carbon dioxidecontent of a gas mixture exiting from the mixer, (e) carbon dioxidecontent of gas mixture in the vicinity of the mix apparatus, (f)temperature of the cement mix or a component of the mix apparatus incontact with the cement mix, (g) rheology of the cement mix, (h)moisture content of the cement mix, or (i) pH of the cement mix. Incertain embodiments, the characteristic monitored by the sensorcomprises carbon dioxide content of a gas mixture exiting from themixer; this can be monitored by a single sensor or by a plurality ofsensors placed at various leak locations, in which case the controlleruses information from the plurality of sensors. The controller can beconfigured to send a signal to the actuator to modulate the flow ofcarbon dioxide when the carbon dioxide content of the gas mixturereaches a threshold value. Alternatively, or in addition, the controllercan be configured to send a signal to the actuator to modulate the flowof carbon dioxide when a rate of change of the carbon dioxide content ofthe gas mixture reaches a threshold value. In certain embodiments, thecharacteristic monitored by the sensor comprise the temperature of thecement mix or a component of the mix apparatus in contact with thecement mix. The controller can be configured to send a signal to theactuator to modulate the flow of carbon dioxide when the temperature ofthe cement mix or a component of the mix apparatus in contact with thecement mix reaches a threshold value. Alternatively, or in addition, thecontroller can be configured to send a signal to the actuator tomodulate the flow of carbon dioxide when a rate of change of thetemperature of the cement mix or a component of the mix apparatus incontact with the cement mix reaches a threshold value.

In certain embodiments, the apparatus comprises a plurality of sensorsconfigured to monitor a plurality of characteristics a plurality ofcharacteristics of the cement binder, the cement mix, a gas mixture incontact with the cement mix or the mixer, or a component of the cementmix apparatus e.g., at least 2, 3, 4, 5, 6, 7, 8, 9, or 10characteristics, for example, at least 2 of (i) mass of cement binderadded to the cement mix, (ii) location of the cement binder in themixer, (iii) carbon dioxide content of a gas mixture within the mixer incontact with the cement mix, (iv) carbon dioxide content of gas mixtureexiting from the mixer, (v) carbon dioxide content of gas mixture in thevicinity of the mixer, (vi) temperature of the cement mix or a componentin contact with the cement mix, (vii) rheology of the cement mix, (viii)moisture content of the cement mix. In certain embodiments, a pluralityof sensors is configured and positioned to monitor at least 3 of (i)mass of cement binder added to the cement mix, (ii) location of thecement binder in the mixer, (iii) carbon dioxide content of a gasmixture within the mixer in contact with the cement mix, (iv) carbondioxide content of gas mixture exiting from the mixer, (v) carbondioxide content of gas mixture in the vicinity of the mixer, (vi)temperature of the cement mix or a component in contact with the cementmix, (vii) rheology of the cement mix, (viii) moisture content of thecement mix. In certain embodiments, a plurality of sensors is configuredand positioned to monitor at least 4 of (i) mass of cement binder addedto the cement mix, (ii) location of the cement binder in the mixer,(iii) carbon dioxide content of a gas mixture within the mixer incontact with the cement mix, (iv) carbon dioxide content of gas mixtureexiting from the mixer, (v) carbon dioxide content of gas mixture in thevicinity of the mixer, (vi) temperature of the cement mix or a componentin contact with the cement mix, (vii) rheology of the cement mix, (viii)moisture content of the cement mix. In certain embodiments, a pluralityof sensors is configured and positioned to monitor at least 5 of (i)mass of cement binder added to the cement mix, (ii) location of thecement binder in the mixer, (iii) carbon dioxide content of a gasmixture within the mixer in contact with the cement mix, (iv) carbondioxide content of gas mixture exiting from the mixer, (v) carbondioxide content of gas mixture in the vicinity of the mixer, (vi)temperature of the cement mix or a component in contact with the cementmix, (vii) rheology of the cement mix, (viii) moisture content of thecement mix. In certain embodiments, a plurality of sensors is configuredand positioned to monitor at least 6 of (i) mass of cement binder addedto the cement mix, (ii) location of the cement binder in the mixer,(iii) carbon dioxide content of a gas mixture within the mixer incontact with the cement mix, (iv) carbon dioxide content of gas mixtureexiting from the mixer, (v) carbon dioxide content of gas mixture in thevicinity of the mixer, (vi) temperature of the cement mix or a componentin contact with the cement mix, (vii) rheology of the cement mix, (viii)moisture content of the cement mix.

In addition to these sensors, or alternatively, the apparatus mayinclude one or more sensors to monitor the time of exposure of thecement mix to the carbon dioxide, the flow rate of the carbon dioxide,or both. For example, a sensor may signal when a valve to supply carbondioxide has opened, and, e.g., the flow rate of the carbon dioxide, anda timer circuit in the controller can determine total carbon dioxidedose.

Sensors may be wired to the controller or may transmit informationwirelessly, or any combination thereof.

The apparatus may additionally, or alternatively, include an actuatorconfigured to modulate an additional characteristic of the mixoperation, where the actuator is operably connected to the controllerand wherein the controller is configured to send a signal to theactuator to modulate the additional characteristic based on theprocessing of information from one or more sensors. This actuator can beconfigured to modulate addition of admixture to the cement mix, type ofadmixture added to the cement mix, timing of addition of admixture tothe cement mix, amount of admixture added to the cement mix, amount ofwater added to the cement mix, timing of addition of water to the cementmix, or cooling the cement mix during or after carbon dioxide addition.In certain embodiments, the apparatus comprises a plurality of suchactuators, such as at least 2, 3, 4, 5, 6, 7, or 8 such actuators.

The actuators may be wired to the controller, or may receive signalsfrom the controller wirelessly.

The controller may be any suitable controller so long as it is capableof being configured to receive information from one or more sensors,process the information to determine if an output is required, andtransmit signals to one or more actuators, as necessary, based on theprocessing; e.g., a computer. For example, the controller can be aProgrammable Logic Controller (PLC), optionally with a Human MachineInterface (HMI), as described elsewhere herein. The controller may belocated onsite with the mixer, or it may be remote, e.g., a physicalremote controller or a Cloud-based controller. In certain embodiments,the controller is configured to store and process the informationobtained regarding the characteristic monitored by the sensor for afirst batch of cement mix and to adjust conditions for a subsequentsecond cement mix batch based on the processing to optimize one or moreaspects of the mix operation. For example, the controller may adjust thesecond mix recipe, e.g., amount of water used or timing of wateraddition, or carbon dioxide exposure in the second batch to improvecarbon dioxide uptake, or to improve rheology or other characteristicsof the mix. In such embodiments in which one or more conditions of asecond mix operation are adjusted, in certain embodiments the one ormore conditions of the second mix operation includes (a) total amount ofcarbon dioxide added to the cement mix, (b) rate of addition of carbondioxide, (c) time of addition of carbon dioxide to the cement mix, (d)whether or not an admixture is added to the cement mix, (e) type ofadmixture added to the cement mix, (f) timing of addition of admixtureto the cement mix, (g) amount of admixture added to the cement mix, (h)amount of water added to the cement mix, (i) timing of addition of waterto the cement mix, (j) cooling the cement mix during or after carbondioxide addition, or a combination thereof. The controller can alsoreceive additional information regarding one or more characteristics ofthe cement mix measured after the cement mix leaves the mixer, andadjusts conditions for the second cement mix batch based on processingthat further comprises the additional information. In certainembodiments, the one or more characteristics of the cement mix measuredafter the cement mix leaves the mixer comprises (a) rheology of thecement mix at one or more time points, (b) strength of the cement mix atone or more time points, (c) shrinkage of the cement mix, (d) waterabsorption of the cement mix, or a combination thereof. Othercharacteristics include water content, carbon dioxide analysis toconfirm carbon dioxide uptake, calcite content (e.g., as determined byinfrared spectroscopy), elastic modulus, density, and permeability. Anyother suitable characteristic may be measured.

In embodiments in which a controller adjusts conditions for a second mixoperation based on input from a first mix operation, the second mixoperation may be in the same mix facility or it may be in a differentmix facility. In certain embodiments, the controller, one or moresensors, one or more actuators, or combination thereof, transmitsinformation regarding the characteristics monitored and conditionsmodulated to a central controller that receives information from aplurality of controllers, sensors, actuators, or combination thereof,each of which transmits information from a separate mixer and mixoperation to the central controller. In these embodiments, the apparatusmay include a second controller that is the central controller, or thecentral controller may be the only controller for the apparatus. Thus,for example, a first mix facility may have a first sensor to monitor afirst characteristic of the first mix operation, and a second mixfacility may have a second sensor to monitor a second characteristic ofa second mix operation, and both may send information regarding thefirst and second characteristics to a central controller, whichprocesses the information and transmit a signal to the first, second, oreven a third, fourth, fifth, etc., mix operation to adjust conditionsbased on the first and second signals from the first and second sensors.Additional information that will be typically transmitted to the centralcontroller includes mix components for the mixes at the first and secondmix operations (e.g., type and amount of cement binder, amount of waterand w/c ratio, types and amounts of aggregate, whether aggregate was wetor dry, admixtures, and the like) amount, rate, and timing of carbondioxide addition, and any other characteristic of the first and secondmix operations that would be useful for determining conditions tomodulate future mix operations based on the characteristics achieved inpast mix operations. Any number of mix operations may input informationto the central controller, e.g., at least 2, 3, 4, 5, 6, 7, 8, 9, or 10mix operations, or at least 15, 20, 25, 30, 40, 50, 60, 70, 80, 90, or100 mix operations. The central controller may also receive any otherinformation that may be suitable to informing decisions regarding mixoperations to optimize one or more conditions of the mix operationand/or of the cement mix produced in the operation. For example, thecentral controller may receive information from experiments conductedwith various types of cements (e.g., various types of Portland cements)carbonated under various conditions, and/or exposed to variousadmixtures, such as at different times, or in different concentrations,and the like, and the resulting characteristics of the cement mix, suchas rheology at one or more timepoints, strength at one or moretimepoints, and the like. Any other suitable information, such asinformation published in literature, or obtained in any manner, may beinput into the central controller, e.g., automatically and/or through aHuman Machine Interface. The information the central controller receivescan be processed and used to adjust cement mix operations at any mixoperation to which the central controller can transmit outputs. Thus,the central controller can learn from numerous mix operations tooptimize future operations and, over time, can accumulate a database toinform decisions in mix operations at a mix site even if a particularmix recipe and/or conditions have never been used at that site, or evenpredict optimum conditions for a mix recipe that has not been used atany of the sites to which the controller is connected. The centralcontroller can match to past mix recipes, or predict optimum conditionsfor a new mix recipe based on suitable algorithms using information inits database, or both.

In certain embodiments in which the controller adjusts a second mixoperation based on characteristics monitored in a first mix operation,the one or more characteristics of the mix operation may comprise totalamount of carbon dioxide added to the cement mix, rate of addition ofcarbon dioxide, time of addition of carbon dioxide to the cement mix,whether or not an admixture is added to the cement mix, type ofadmixture added to the cement mix, timing of addition of admixture tothe cement mix, amount of admixture added to the cement mix, amount ofwater added to the cement mix, timing of addition of water to the cementmix, cooling the cement mix during or after carbon dioxide addition, ora combination thereof.

The controller can be further configured, e.g., programmed, to receiveand process information regarding one or more characteristics of thecement mix measured after the cement mix leaves the mixer, and totransmit signals to one or more actuators configured to adjustconditions for the second cement mix batch based on the processing toimprove contact with the carbon dioxide or another characteristic of themix operation in the second mix operation. The one or morecharacteristics of the cement mix measured after the cement mix leavesthe mixer can be rheology of the cement mix at one or more time points,strength of the cement mix at one or more time points, water absorption,shrinkage, and the like. The characteristic monitored can depend on therequirements for a particular mix batch, although other characteristicsmay also be monitored to provide data to the controller for futurebatches in which those characteristics would be required.

The use of an apparatus that includes a control system, whether for asingle mix operation or for a plurality of mix operations, can producevery high efficiencies of carbon dioxide uptake (ratio of carbon dioxideor carbon dioxide derivatives in the cement mix to total carbon dioxidedelivered). In certain embodiments, the apparatus is configured tocontrol one or more actuators such that an efficiency of carbonation ofat least 60, 70, 80, 90, 95, 96, 97, 98, 99, or 99.5% is achieved. Suchhigh efficiencies allow for greater sequestration of greenhouse gaswithout leakage into the atmosphere, as well as a more economicaloperation.

In certain embodiments, the invention provides a controller forcontrolling a cement mix mixing operation comprising carbonation of thecement mix in a mixer by exposing the cement mix to carbon dioxide,where the controller comprises (i) an input port for receiving a signalfrom a sensor that monitors a characteristic of the cement mix mixingoperation; (ii) a processor for processing the signal from the sensorand formulating an output signal to modulate the exposure of the cementmix to carbon dioxide or to modulate a characteristic of the cement mix;and (iii) an output port for transmitting the output signal to anactuator that modulates the exposure of the cement mix to carbon dioxideor that modulates a characteristic of the cement mix. The input andoutput ports may be configured to be wired to the sensor or actuator, orto receive a wireless signal, or a combination of such ports may beused. In certain embodiments, the input port is configured to receive aplurality of signals from a plurality of sensors, and the processor isconfigured to process the plurality of signals and formulate an outputsignal to modulate the exposure of the cement mix to carbon dioxide orto modulate a characteristic of the cement mix. Thus, the input port mayinclude a plurality separate ports that are wired to various sensors, ora wireless port that is configured to receive signals from a pluralityof sensors, or a combination of one or more wired and wireless ports forone or more sensors. The controller can be is configured to formulate aplurality of output signals to modulate the exposure of the cement mixto carbon dioxide or to modulate a characteristic of the cement mix andthe output port is configured to transmit the plurality of signals.Similar to an input port for a plurality of signals, this can be a wiredoutput port with a plurality of ports, a wireless port configured tosend a plurality of signals, or a combination of wired and wirelessports to send one or more signals each.

The controller may be configured to process any signal from any suitablesensor, such as described herein, and to send output to any suitableactuator, such as described herein. The controller may also beconfigured to send information to a central controller, or may itself bea central controller that is configured to receive input from, and sendoutput to, a plurality of mix operations, also as described herein.

In certain embodiments, the invention provides a network comprising aplurality of spatially separate cement mix operations, such as at least2, 3, 4, 5, 6, 7, 8, 9, or 10, or at least 20, 30, 40, 50, 70, or 100separate mix operations, each of which comprises at least one sensor formonitoring at least one characteristic of its operation, and comprisinga central processing unit, to which each sensor sends its informationand which stores and/or processes the information. Alternatively, or inaddition, information regarding at least one characteristic of the mixoperation may be input manually into the central processing unit, e.g.,through a HMI. One or more of the mix operations may be a mix operationin which the cement mix is carbonated, e.g., as described herein, suchas a mix operation in which the cement is carbonated, i.e., exposed tocarbon dioxide in such a way that the carbon dioxide is taken up by thecement mix, during mixing. The mix operations may also include sensorsor other elements by which one or more characteristics of the cement mixis monitored, before, during, or after mixing, e.g., also as describedherein, which transmit information to the central processor. The centralprocessor may also be configured to output signals to one or more of themix operations, or to other mix operations, based on the processing ofthe signals.

In certain embodiments, the invention provides an apparatus forproducing a cement mix, e.g., hydraulic cement mix comprising (i) amixer for mixing a cement mix, e.g., hydraulic cement mix; and (ii) asystem for exposing the cement mix, e.g., hydraulic cement mix to carbondioxide during mixing, wherein the system is configured to delivercarbon dioxide to the surface of the cement mix, e.g., hydraulic cementmix.

In certain embodiments, the invention provides an apparatus for mixing acement mix, e.g., hydraulic cement mix comprising (i) a mixer for mixingthe cement mix, e.g., hydraulic cement mix; (ii) a system for contactingthe cement mix, e.g., hydraulic cement mix with carbon dioxide directedto the cement mix, e.g., hydraulic cement mix operably connected to themixer; (iii) a sensor positioned and configured to monitor one or morecharacteristics of the cement mix, e.g., hydraulic cement mix, a gasmixture in contact with the cement mix, e.g., hydraulic cement mix, acomponent of a cement mix, e.g., hydraulic cement mix apparatus, or acomponent exposed to the cement mix, e.g., hydraulic cement mix; and(iv) an actuator operably connected to the sensor for modulating theflow of the carbon dioxide based on the characteristic monitored. Incertain aspects of this embodiment, the system for contacting the cementmix, e.g., hydraulic cement mix with carbon dioxide comprises a system asystem for contacting the cement mix, e.g., hydraulic cement mix with aflow of carbon dioxide directed to the cement mix, e.g., hydrauliccement mix.

In certain embodiments, the invention provides an apparatus forretrofitting an existing cement mix, e.g., hydraulic cement mixercomprising a conduit configured to be operably connected to a source ofcarbon dioxide and to the mixer, for delivering carbon dioxide from thesource to the mixer. The apparatus may comprise the source of carbondioxide. The apparatus may comprise an actuator for controlling deliveryof carbon dioxide from a source of carbon dioxide through the conduit,wherein the actuator is operably connected or is configured to beoperably connected to a control system. The apparatus may furthercomprise the control system. The control system may comprise a timer anda transmitter for sending a signal to the actuator based on the timingof the timer. The control system may be an existing control system forthe mixer. The apparatus may comprise instructions for modifying theexisting control system to control the actuator. The actuator may beoperably connected to or configured to be operably connected to theconduit, the mixer, a control system for the mixer, or to a source ofcarbon dioxide, or a combination thereof. The actuator may control avalve so as to control delivery of carbon dioxide to the mixer. Theapparatus may comprise one or more sensors operably connected to, orconfigured to be operably connected to, the control system formonitoring one or more characteristics of the cement mix, e.g.,hydraulic cement mix, a gas mixture adjacent to the cement mix, e.g.,hydraulic cement mix, or a component in contact with the cement mix,e.g., hydraulic cement mix. The one or more sensors may be a sensor formonitoring carbon dioxide concentration of a gas or a temperature.

In certain embodiments, the invention provides a system for exposing acement mix, e.g., hydraulic cement mix within a transportable mixer tocarbon dioxide comprising (i) a source of carbon dioxide that is morethan 50% pure carbon dioxide; (ii) a transportable mixer for mixing acement mix, e.g., hydraulic cement mix; and (iii) a conduit operablyconnected to the source of carbon dioxide and to the mixer fordelivering carbon dioxide from the source of carbon dioxide to thecement mix, e.g., hydraulic cement mix. The system may further comprisean actuator operably connected to the conduit for controlling the flowof the carbon dioxide. The actuator may comprise a valve. The system maycomprise a controller operably connected to the actuator, where thecontroller is configured to operate the actuator based on predeterminedparameters, on feedback from one or more sensors, or a combinationthereof. In certain embodiments the source of carbon dioxide and theconduit are housed in a portable unit that can be moved from onereadymix site to another, to provide carbon dioxide to more than onereadymix truck.

In certain embodiments, the invention provides a system for exposing acement mix, e.g., hydraulic cement mix within a mixer to carbon dioxidecomprising (i) a source of carbon dioxide; (ii) the mixer for mixing thecement mix, e.g., hydraulic cement mix; (iii) a conduit operablyconnected to the source of carbon dioxide and to the mixer fordelivering carbon dioxide from the source of carbon dioxide to thecement mix, e.g., hydraulic cement mix; (iv) a sensor positioned andconfigured to monitor one or more one or more characteristics of thecement mix, e.g., hydraulic cement mix, a gas mixture adjacent to thecement mix, e.g., hydraulic cement mix, or a component in contact withthe cement mix, e.g., hydraulic cement mix; and (v) an actuator operablyconnected to the sensor and to the system for exposing the cement mix,e.g., hydraulic cement mix to carbon dioxide, wherein the actuator isconfigured to alter the exposure of the cement mix, e.g., hydrauliccement mix to the carbon dioxide based on the characteristic monitoredby the sensor. The mixer may be a stationary mixer. The mixer may be atransportable mixer.

V. Compositions

The invention also provides compositions, e.g., compositions that may beproduced by the methods described herein. In certain embodiment theconcrete mix is fluid, that is, capable of being mixed in the mixer andpoured for its intended purpose. In certain embodiments the inventionprovides a composition that is a dry carbonated concrete mix that isfluid and compactable, e.g., sufficiently fluid and compactable to beplaced in a mold for a pre-cast concrete product, that compriseshydraulic cement, e.g., OPC, and carbon dioxide and/or reaction productsof carbon dioxide with the OPC and/or other components of the mix, and,optionally, one or more of aggregates and an admixture, such as anadmixture to modulate the compactability of the carbonated concrete mix,and/or a strength accelerator. In certain embodiments the admixturecomprises a set retarder, such as a sugar or sugar derivative, e.g.,sodium gluconate. In certain embodiments the invention provides acomposition that is a wet carbonated concrete mix that is fluid andpourable, e.g., sufficiently fluid and pourable to be poured in a moldat a construction site, that comprises hydraulic cement, e.g., OPC, andcarbon dioxide and/or reaction products of carbon dioxide with the OPCand/or other components of the mix, and, optionally, one or more ofaggregates and an admixture, such as an admixture to modulate theflowability of the carbonated concrete mix, and/or a strengthaccelerator. In certain embodiments the admixture comprises a setretarder, such as a sugar or sugar derivative, e.g., sodium gluconate.

In some methods, solid carbon dioxide (dry ice) is added to the cementmix, producing a composition comprising a cement mix, such as ahydraulic cement mix such as concrete, and solid carbon dioxide. Thesolid carbon dioxide may be present in an amount of greater than 0.01,0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3,1.4, 1.5, 1.7, 2.0, or 2.5% bwc, or 0.01-5%, 0.01-2%, 0.01-1%,0.01-0.5%, 0.1-5%, 0.1-2%, 0.1-1%, or 0.1-0.5%. In certain embodimentsthe invention provides a cement mix comprising gaseous carbon dioxide orcarbon dioxide reaction products, such as carbonates, and solid carbondioxide. The solid carbon dioxide may be present in an amount of greaterthan 0.01, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1,1.2, 1.3, 1.4, 1.5, 1.7, 2.0, or 2.5% bwc or 0.01-5%, 0.01-2%, 0.01-1%,0.01-0.5%, 0.1-5%, 0.1-2%, 0.1-1%, or 0.1-0.5%. The gaseous carbondioxide or carbon dioxide reaction products may be present in an amountof greater than 0.01, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9,1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.7, 2.0, or 2.5% bwc, or 0.01-5%,0.01-2%, 0.01-1%, 0.01-0.5%, 0.1-5%, 0.1-2%, 0.1-1%, or 0.1-0.5%. Carbondioxide reaction products include carbonic acid, bicarbonate, and allforms of calcium carbonate (e.g., amorphous calcium carbonate, vaterite,aragonite, and calcite), as well as other products formed by thereaction of carbon dioxide with various components of the cement mix.The solid carbon dioxide may be added as a single block, or more thanone block, such as more than 2, 3, 4, 5, 6, 7, 8, 9, 10, 20, 50, or 100blocks. In some embodiments, the solid carbon dioxide is formed fromrelease of liquid carbon dioxide into the mix.

The cement mix may contain an admixture, such as any admixture asdescribed herein, e.g., a carbohydrate or carbohydrate derivative, suchas sodium gluconate. The admixture may be present in an amount ofgreater than 0.01, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9,1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.7, 2.0, or 2.5%; or greater than 0.01,0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3,1.4, 1.5, 1.7, 2.0, or 2.5% and less than 0.05, 0.1, 0.2, 0.3, 0.4, 0.5,0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.7, 2.0, 2.5 or 3.0%,e.g., any range that may be expressed as the greater than and less thanamounts. Exemplary ranges include 0.01-3.0%, 0.01-1.5%, 0.01-1%,0.01-0.5%, 0.01-0.4%, 0.01-0.2%, 0.01-0.1%, 0.1-3.0%, 0.1-1.5%, 0.1-1%,0.1-0.5%, 0.1-0.4%, 0.1-0.2%, or 0.1-0.1%.

It has been found that the addition of carbon dioxide to a cement mixduring mixing results in the formation of nanocrystals of calciumcarbonate. Earlier work has shown that adding exogenous nanocrystallinecalcium carbonate (e.g., calcium carbonate with a particle size in arange of 50-120 nm) to a concrete mix improved the hydration of the mix;however, when exogenously supplied calcium carbonate is used, a largequantity, such as 10% bwc, is needed to achieve the desired effect,probably due to clumping of the added nanocrystals. In contrast, thecalcium carbonate nanocrystals can be formed in situ, without clumping,and thus a much greater dispersion can be achieved; i.e., homogeneouslydispersed nanocrystals as opposed to dispersion with clumping. Withoutbeing bound by theory, it is possible that the performance improvementobserved due to the formation of carbonate reaction products in somecarbonate concrete mixes is analogous to growing an in-situ nanoparticleCaCO₃ addition that would act as nucleation sites and impact laterhydration product development.

Thus, for example, in certain embodiments, the incidence of discretesingle nanocrystals of calcium carbonate of less than 500 nm, or lessthan 400 nm, or less than 300 nm, or less than 200 nm particle size,such as homogenously dispersed nanocrystals without clumping, or withoutsubstantial clumping, may be over 10, 20, 30, 40, 50, 60, or 80% of thecalcium carbonate in the composition. “Particle size” refers to lengthof the longest dimension of the crystals, and may be determined, e.g.,by scanning electron microscopy. The calcium carbonate may comprise lessthan 5%, 4%, 3%, 2.5%, 2.0%, 1.9%, 1.8%, 1.7%, 1.6% 1.5%, 1.4%, 1.3%,1.2%, 1.1%, 1.0%, 0.9%, 0.8%, 0.7%, 0.6%, 0.5%, 0.4%, 0.3%, 0.2%, or0.1% bwc of the composition, e.g., cement mix composition such as ahydraulic cement mix, e.g., concrete composition, in certain embodimentscomprising, e.g., also comprising, at least 0.001%, 0.01%, 0.1%, 0.2%,0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%,1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.7%,3.0%, or 4.0% bwc of the composition, e.g., cement mix composition suchas a hydraulic cement mix, e.g., concrete composition. For example, incertain embodiments the calcium carbonate comprises 0.001-5.0% bwc ofthe composition; in certain embodiments the calcium carbonate comprises0.001-4.0% bwc of the composition; in certain embodiments the calciumcarbonate comprises 0.001-3.0% bwc of the composition; in certainembodiments, the calcium carbonate comprises 0.001-2.5% bwc of thecomposition; in certain embodiments the calcium carbonate comprises0.001-2.0% bwc of the composition; in certain embodiments the calciumcarbonate comprises 0.001-1.5% bwc of the composition; in certainembodiments the calcium carbonate comprises 0.001-1.3% bwc of thecomposition; in certain embodiments the calcium carbonate comprises0.001-1.0% bwc of the composition; in certain embodiments the calciumcarbonate comprises 0.001-0.8% bwc of the composition; in certainembodiments the calcium carbonate comprises 0.001-0.6% bwc of thecomposition; in certain embodiments the calcium carbonate comprises0.001-0.5% bwc of the composition; in certain embodiments the calciumcarbonate comprises 0.001-0.4% bwc of the composition; in certainembodiments the calcium carbonate comprises 0.001-0.3% bwc of thecomposition; in certain embodiments the calcium carbonate comprises0.001-0.2% bwc of the composition; in certain embodiments the calciumcarbonate comprises 0.001-0.1% bwc of the composition; in certainembodiments the calcium carbonate comprises 0.01-5.0% bwc of thecomposition; in certain embodiments the calcium carbonate comprises0.01-4.0% bwc of the composition; in certain embodiments the calciumcarbonate comprises 0.01-3.0% bwc of the composition; in certainembodiments the calcium carbonate comprises 0.01-2.5% bwc of thecomposition; in certain embodiments the calcium carbonate comprises0.01-2.0% bwc of the composition; in certain embodiments the calciumcarbonate comprises 0.01-1.5% bwc of the composition; in certainembodiments the calcium carbonate comprises 0.01-1.3% bwc of thecomposition; in certain embodiments the calcium carbonate comprises0.01-1.0% bwc of the composition; in certain embodiments the calciumcarbonate comprises 0.01-0.8% bwc of the composition; in certainembodiments the calcium carbonate comprises 0.01-0.6% bwc of thecomposition; in certain embodiments the calcium carbonate comprises0.01-0.4% bwc of the composition; in certain embodiments the calciumcarbonate comprises 0.01-0.3% bwc of the composition; in certainembodiments the calcium carbonate comprises 0.01-0.2% bwc of thecomposition; in certain embodiments the calcium carbonate comprises0.01-0.1% bwc of the composition; in certain embodiments the calciumcarbonate comprises 0.1-5.0% bwc of the composition; in certainembodiments the calcium carbonate comprises 0.1-4.0% bwc of thecomposition; in certain embodiments the calcium carbonate comprises0.1-3.0% bwc of the composition; in certain embodiments the calciumcarbonate comprises 0.1-2.5% bwc of the composition; in certainembodiments the calcium carbonate comprises 0.1-2.0% bwc of thecomposition; in certain embodiments the calcium carbonate comprises0.1-1.5% bwc of the composition; in certain embodiments the calciumcarbonate comprises 0.1-1.3% bwc of the composition; in certainembodiments the calcium carbonate comprises 0.1-1.0% bwc of thecomposition; in certain embodiments the calcium carbonate comprises0.1-0.8% bwc of the composition; in certain embodiments the calciumcarbonate comprises 0.1-0.6% bwc of the composition; in certainembodiments the calcium carbonate comprises 0.1-0.4% bwc of thecomposition; in certain embodiments the calcium carbonate comprises0.1-0.3% bwc of the composition; in certain embodiments the calciumcarbonate comprises 0.1-0.2% bwc of the composition. In certainembodiments, the composition is a concrete composition comprisinghydraulic cement, e.g., Portland cement, and aggregate, where thehydraulic cement comprises less than 35%, 30%, 25%, 23%, 20%, 18%, 15%,13%, or 10% by weight of the concrete composition, in certainembodiments comprising, e.g., also comprising, at least 5%, 8%, 10%,13%, 15%, 20%, 23%, 25%, or 30% by weight of the concrete composition.For example, in certain embodiments the hydraulic cement comprises 5-35%by weight of the concrete composition; in certain embodiments thehydraulic cement comprises 5-30% by weight of the concrete composition;in certain embodiments the hydraulic cement comprises 5-25% by weight ofthe concrete composition; in certain embodiments the hydraulic cementcomprises 5-23% by weight of the concrete composition; in certainembodiments the hydraulic cement comprises 5-20% by weight of theconcrete composition; in certain embodiments the hydraulic cementcomprises 5-18% by weight of the concrete composition; in certainembodiments the hydraulic cement comprises 5-15% by weight of theconcrete composition; in certain embodiments the hydraulic cementcomprises 10-35% by weight of the concrete composition; in certainembodiments the hydraulic cement comprises 10-30% by weight of theconcrete composition; in certain embodiments the hydraulic cementcomprises 10-25% by weight of the concrete composition; in certainembodiments the hydraulic cement comprises 10-23% by weight of theconcrete composition; in certain embodiments the hydraulic cementcomprises 10-20% by weight of the concrete composition; in certainembodiments the hydraulic cement comprises 10-18% by weight of theconcrete composition; in certain embodiments the hydraulic cementcomprises 10-15% by weight of the concrete composition; in certainembodiments the hydraulic cement comprises 15-35% by weight of theconcrete composition; in certain embodiments the hydraulic cementcomprises 15-30% by weight of the concrete composition; in certainembodiments the hydraulic cement comprises 15-25% by weight of theconcrete composition; in certain embodiments the hydraulic cementcomprises 15-23% by weight of the concrete composition; in certainembodiments the hydraulic cement comprises 15-20% by weight of theconcrete composition; in certain embodiments the hydraulic cementcomprises 15-18% by weight of the concrete composition. The compositionmay be a wet concrete composition, for example, a flowable concretecomposition, or it may be a concrete composition that has undergone setand/or hardening. In certain embodiment, it can be assumed for purposesof determining calcium carbonate content of a composition that allcarbon dioxide in the composition has been converted to calciumcarbonate, and that a value from a test for carbonation can be convertedto a calcium carbonate value; for example, if a test of carbonation fora concrete mix shows an uptake of carbon dioxide of 0.6% bwc, it can beassumed that the composition is 1.4% bwc of calcium carbonate. Anysuitable test for carbonation may be used, such as those describedherein.

As crystal formation starts, crystal size for at least 10, 20, 30, 40,or 50% of the calcium carbonate in the composition may be less 100, 80,60, 50, 40, or 30 nm. In addition, the polymorphic composition of thecrystals may vary, depending on the time the composition has beenreacting, the timing of addition of carbon dioxide, the use ofcrystal-modifying admixtures, and the like. In certain embodiments, atleast 1, 5, 10, 20, 30, 40, or 50% of the calcium carbonate in thecomposition is amorphous calcium carbonate, or 0.01-50%, 0.1-50%, 1-50%,5-50%, 10-50%, or 20-50%. In certain embodiments, at least 1, 5, 10, 20,30, 40, or 50% of the calcium carbonate in the composition is vaterite,0.01-50%, 0.1-50%, 1-50%, 5-50%, 10-50%, or 20-50%. In certainembodiments, at least 1, 5, 10, 20, 30, 40, or 50% of the calciumcarbonate in the composition is aragonite, 0.01-50%, 0.1-50%, 1-50%,5-50%, 10-50%, or 20-50%. In certain embodiments, at least 1, 5, 10, 20,30, 40, or 50% of the calcium carbonate in the composition is calcite,or 0.01-99.9%, 0.1-99.9%, 1-99%, 5-99.9%, 10-99.9%, 30-99.9%, 50-99.9%,0.01-90%, 0.1-90%, 1-90%, 5-90%, 10-90%, 30-90%, 50-90%, 0.01-80%,0.1-80%, 1-80%, 5-80%, 10-80%, 30-80%, 50-80%. Any combination ofamorphous calcium carbonate, vaterite, aragonite, and/or calcite mayalso be present, for example at the indicated percentages.

Compositions may also include one or more supplementary cementitiousmaterials (SCMs) and/or cement replacements, as described elsewhereherein. In certain embodiments, a composition includes, in addition tocement, one or more SCMS and/or cement replacements, for example blastfurnace slag, fly ash, silica fume, natural pozzolans (such asmetakaolin, calcined shale, calcined clay, volcanic glass, zeolitictrass or tuffs, rice husk ash, diatomaceous earth, and calcined shale),waste glass, limestone, recycled/waste plastic, scrap tires, municipalsolid waste ash, wood ash, cement kiln dust, or foundry sand, at asuitable percentage of the composition bwc, such as 0.1-100%, or 1-100%,or 5-100%, or 10-100%, or 20-100%, or 30-100%, or 40-100%, or 50-100%,or 0.1-80%, or 1-80%, or 5-80%, or 10-80%, or 20-80%, or 30-80%, or40-80%, or 50-80%, or 0.1-50%, or 1-50%, or 5-50%, or 10-50%, or 20-50%,or 30-50%, or 0.1-40%, or 1-40%, or 5-40%, or 10-40%, or 20-40% bwc. Incertain embodiments, the composition includes an SCM and in some ofthese embodiments the SCM is fly ash, slag, silica fume, or a naturalpozzolan. In certain embodiment, the SCM is fly ash. In certainembodiments, the SCM is slag. Further embodiments in which SCM is usedare described elsewhere herein.

Thus, in certain embodiments, the invention provides a fluid cement mix,e.g., hydraulic cement mix composition comprising (i) a wet cement mix,e.g., hydraulic cement mix comprising hydraulic cement and water in aw/c ratio of no more than 0.4, or 0.3, or 0.2 and (ii) carbon dioxide orcarbonation product in an amount of at least 0.05% by weight of cement(bwc). The composition is in a mixable and/or flowable state, e.g., setand hardening have not progressed to the point where the mixture can nolonger be mixed by the apparatus in which it is formed. The compositionmay further comprise (ii) an admixture for modulating the flowability ofthe cement mix, e.g., hydraulic cement mixture. The admixture may apolycarboxylate superplasticer, a naphthalene HRWR, or a combinationthereof.

In certain embodiments, the invention provides a fluid cement mix, e.g.,hydraulic cement mix composition comprising (i) a wet cement mix, e.g.,hydraulic cement mix comprising hydraulic cement and water; (ii) carbondioxide or carbonation product in an amount of at least 0.05% bwc; (iii)an admixture for modulating the flowability of the wet hydraulic cementmix. In certain embodiments the admixture comprises a polycarboxylatesuperplasticer, a naphthalene HRWR, or any combination thereof.

In certain embodiments, the invention provides a cement mix, e.g.,hydraulic cement mix composition, which may be a fluid cement mix,comprising (i) a wet cement mix, e.g., hydraulic cement mix comprisinghydraulic cement and water; (ii) carbon dioxide in solid, liquid, and/orgaseous form, or in aqueous solution as carbonic acid or bicarbonate, inan amount of 0.01-2% bwc; (iii) solid calcium carbonate in an amount of0.01-2% bwc; and (iii) a supplementary cementitious material and/orcement replacement. In certain embodiments, the carbon dioxide comprisescarbon dioxide in solid form. During mixing and later set and hardening,various intermediate compositions are produced, so that initialcompositions may contain mostly carbon dioxide in gaseous, liquid, solidform or in solution with little calcium carbonate formation, and latercompositions may contain mostly calcium carbonate with little carbondioxide in gaseous, liquid, solid form or in solution. In certainembodiments, the SCM and/or cement replacement comprises 0.1-50%, or1-50%, or 5-50%, or 10-50%, or 20-50%, or 1-40%, or 5-40%, or 10-50%, or20-40% bwc in the composition. In certain embodiments, the SCM and/orcement replacement is blast furnace slag, fly ash, silica fume, naturalpozzolans (such as metakaolin, calcined shale, calcined clay, volcanicglass, zeolitic trass or tuffs, rice husk ash, diatomaceous earth, andcalcined shale), limestone, waste glass, recycled/waste plastic, scraptires, municipal solid waste ash, wood ash, cement kiln dust, or foundrysand, or a combination thereof. In certain embodiments, an SCM is usedand in certain of these embodiments, the SCM is blast furnace slag, flyash, silica fume, or natural pozzolan, or a combination thereof. Incertain embodiments, the SCM is blast furnace slag. In certainembodiments, the SCM is fly ash. In certain embodiments, the SCM issilica fume. In certain embodiments, the SCM is a natural pozzolan. Incertain embodiments the hydraulic cement is Portland cement. Thecomposition may further comprise an admixture. In certain embodiments,the admixture is a carbohydrate or carbohydrate derivative, such assodium gluconate. The admixture may be present at any suitableconcentration, such as 0.01-2%, or 0.01-1%, or 0.01-0.5%, or 0.01-0.4%,or 0.01-0.3%, or 0.01-0.2%, or 0.01-0.1%. The polymorphic composition ofthe calcium carbonate may include any of the polymorphs describedherein. In certain embodiments, at least 1, 5, 10, 20, 30, 40, or 50% ofthe calcium carbonate in the composition is amorphous calcium carbonate,or 0.01-50%, 0.1-50%, 1-50%, 5-50%, 10-50%, or 20-50%. In certainembodiments, at least 1, 5, 10, 20, 30, 40, or 50% of the calciumcarbonate in the composition is vaterite, or 0.01-50%, 0.1-50%, 1-50%,5-50%, 10-50%, or 20-50%. In certain embodiments, at least 1, 5, 10, 20,30, 40, or 50% of the calcium carbonate in the composition is aragonite,or 0.01-50%, 0.1-50%, 1-50%, 5-50%, 10-50%, or 20-50%. In certainembodiments, at least 1, 5, 10, 20, 30, 40, or 50% of the calciumcarbonate in the composition is calcite, or 0.01-99.9%, 0.1-99.9%,1-99%, 5-99.9%, 10-99.9%, 30-99.9%, 50-99.9%, 0.01-90%, 0.1-90%, 1-90%,5-90%, 10-90%, 30-90%, 50-90%, 0.01-80%, 0.1-80%, 1-80%, 5-80%, 10-80%,30-80%, 50-80%. Any combination of amorphous calcium carbonate,vaterite, aragonite, and/or calcite may also be present, for example atthe indicated percentages.

In certain embodiments, the invention provides a set or hardened cementmix, e.g., hydraulic cement mix composition such as a set or hardenedconcrete, comprising (i) reaction products formed in a wet cement mix,e.g., hydraulic cement mix comprising hydraulic cement and water, suchas reaction products of a Portland cement mix; (iii) calcium carbonatein an amount of 0.01-5% bwc, or 0.01-2% bwc, where the calcium carbonateis present as crystals or particles wherein at least 10, 20, 50, 70, or90% of the particles are less than 1 um, or less than 500 nm, or lessthan 400 nm, or less than 200 nm in average dimension; and (iii) asupplementary cementitious material and/or cement replacement and/orreaction products of supplementary cementitious material or cementreplacement. In certain embodiments, the SCM and/or cement replacementcomprises 0.1-50%, or 1-50%, or 5-50%, or 10-50%, or 20-50%, or 1-40%,or 5-40%, or 10-50%, or 20-40% bwc in the composition. In certainembodiments, the SCM and/or cement replacement is blast furnace slag,fly ash, silica fume, natural pozzolans (such as metakaolin, calcinedshale, calcined clay, volcanic glass, zeolitic trass or tuffs, rice huskash, diatomaceous earth, and calcined shale), limestone, waste glass,recycled/waste plastic, scrap tires, municipal solid waste ash, woodash, cement kiln dust, or foundry sand, or a combination thereof. Incertain embodiments, an SCM is used and in certain embodiments, the SCMis blast furnace slag, fly ash, silica fume, or natural pozzolan, or acombination thereof. In certain embodiments, the SCM is blast furnaceslag. In certain embodiment, the SCM is fly ash. In certain embodiments,the SCM is silica fume. In certain embodiments, the SCM is a naturalpozzolan. In certain embodiments the hydraulic cement or reactionproducts is Portland cement or Portland cement reaction products. Thecomposition may further comprise an admixture. In certain embodiments,the admixture is a carbohydrate or carbohydrate derivative, such assodium gluconate. The admixture may be present at any suitableconcentration, such as 0.01-2%, or 0.01-1%, or 0.01-0.5%, or 0.01-0.4%,or 0.01-0.3%, or 0.01-0.2%, or 0.01-0.1%. The polymorphic composition ofthe calcium carbonate may include any of the polymorphs describedherein. In certain embodiments, at least 1, 5, 10, 20, 30, 40, or 50% ofthe calcium carbonate in the composition is amorphous calcium carbonate,or 0.01-50%, 0.1-50%, 1-50%, 5-50%, 10-50%, or 20-50%. In certainembodiments, at least 1, 5, 10, 20, 30, 40, or 50% of the calciumcarbonate in the composition is vaterite, or 0.01-50%, 0.1-50%, 1-50%,5-50%, 10-50%, or 20-50%. In certain embodiments, at least 1, 5, 10, 20,30, 40, or 50% of the calcium carbonate in the composition is aragonite,or 0.01-50%, 0.1-50%, 1-50%, 5-50%, 10-50%, or 20-50%. In certainembodiments, at least 1, 5, 10, 20, 30, 40, or 50% of the calciumcarbonate in the composition is calcite, or 0.01-99.9%, 0.1-99.9%,1-99%, 5-99.9%, 10-99.9%, 30-99.9%, 50-99.9%, 0.01-90%, 0.1-90%, 1-90%,5-90%, 10-90%, 30-90%, 50-90%, 0.01-80%, 0.1-80%, 1-80%, 5-80%, 10-80%,30-80%, 50-80%. Any combination of amorphous calcium carbonate,vaterite, aragonite, and/or calcite may also be present, for example atthe indicated percentages.

In certain embodiments, the invention provides a cement mix, e.g.,hydraulic cement mix composition, which may be a fluid cement mix,comprising (i) a wet cement mix, e.g., hydraulic cement mix comprisinghydraulic cement and water; (ii) calcium carbonate that isnanocrystalline where the incidence of discrete single nanocrystals ofless than 500 nm, or less than 400 nm, or less than 300 nm, or less than200 nm, or less than 100 nm, or less than 50 nm particle size is over10, 20, 30, 40, 50, 60, or 80% of the calcium carbonate; and (iii) asupplementary cementitious material and/or cement replacement. It willbe appreciated that the nanocrystalline character of the composition asa whole may be determined by assaying the nanocrystalline character ofone or more representative samples. In certain embodiments, thenanocrystalline calcium carbonate comprises 0.01-5%, or 0.01-2%, or0.01-1%, or 0.01-0.5%, or 0.01-0.4%, or 0.01-0.3%, or 0.01-0.02%, or0.01-0.1% of the composition bwc. In certain embodiments, the SCM and/orcement replacement comprises 0.1-50%, or 1-50%, or 5-50%, or 10-50%, or20-50%, or 1-40%, or 5-40%, or 10-50%, or 20-40% bwc. In certainembodiments, the SCM and/or cement replacement is blast furnace slag,fly ash, silica fume, natural pozzolans (such as metakaolin, calcinedshale, calcined clay, volcanic glass, zeolitic trass or tuffs, rice huskash, diatomaceous earth, and calcined shale), limestone, waste glass,recycled/waste plastic, scrap tires, municipal solid waste ash, woodash, cement kiln dust, or foundry sand, or a combination thereof. Incertain embodiments, an SCM is used and in certain of these embodiments,the SCM is blast furnace slag, fly ash, silica fume, or naturalpozzolan, or a combination thereof. In certain embodiments, the SCM isblast furnace slag. In certain embodiment, the SCM is fly ash. Incertain embodiments, the SCM is silica fume. In certain embodiments, theSCM is a natural pozzolan. In certain embodiments the hydraulic cementis Portland cement. The composition may further comprise an admixture.In certain embodiments, the admixture is a carbohydrate or carbohydratederivative, such as sodium gluconate. The admixture may be present atany suitable concentration, such as 0.01-2%, or 0.01-1%, or 0.01-0.5%,or 0.01-0.4%, or 0.01-0.3%, or 0.01-0.2%, or 0.01-0.1%. The polymorphiccomposition of the nanocrystals may include any of the polymorphsdescribed herein. In certain embodiments, at least 1, 5, 10, 20, 30, 40,or 50% of the calcium carbonate nanocrystals in the composition isamorphous calcium carbonate nanocrystals, or 0.01-50%, 0.1-50%, 1-50%,5-50%, 10-50%, or 20-50%. In certain embodiments, at least 1, 5, 10, 20,30, 40, or 50% of the calcium carbonate nanocrystals in the compositionis vaterite nanocrystals, or 0.01-50%, 0.1-50%, 1-50%, 5-50%, 10-50%, or20-50%. In certain embodiments, at least 1, 5, 10, 20, 30, 40, or 50% ofthe calcium carbonate nanocrystals in the composition is aragonitenanocrystals, 0.01-50%, 0.1-50%, 1-50%, 5-50%, 10-50%, or 20-50%. Incertain embodiments, at least 1, 5, 10, 20, 30, 40, or 50% of thecalcium carbonate nanocrystals in the composition is calcitenanocrystals, or 0.01-99.9%, 0.1-99.9%, 1-99%, 5-99.9%, 10-99.9%,30-99.9%, 50-99.9%, 0.01-90%, 0.1-90%, 1-90%, 5-90%, 10-90%, 30-90%,50-90%, 0.01-80%, 0.1-80%, 1-80%, 5-80%, 10-80%, 30-80%, 50-80%. Anycombination of amorphous calcium carbonate, vaterite, aragonite, and/orcalcite may also be present, for example at the indicated percentages.It will be appreciated that the polymorphic makeup of the composition asa whole may be estimated by the polymorphic makeup of one or morerepresentative samples of the composition.

EXAMPLES Example 1

This example describes contacting a wet hydraulic cement mix (concrete)with carbon dioxide during mixing of the concrete.

A series of tests were conducted to contact wet concrete mix with carbondioxide during mixing of the concrete.

In a first experiment, bagged readymix concrete (Quikrete or Shaw), 20kg was mixed with water in a Hobart mixer. The cement content of theconcrete was not known but was assumed to be 12-14%. A value of 14% wasused in subsequent calculations. 0.957 kg of water, which was 57% of thefinal water, was added for a w/c ratio of 0.34 and the mixer was toppedwith a loose lid. The concrete mix was mixed for 1 minute. Then a gasmixture containing carbon dioxide at a concentration of 99.5%(Commercial grade carbon dioxide from Air Liquide, 99.5% CO2, UN1013,CAS:124-38-9) was delivered to contact the surface of the mixingconcrete via a tube of approximately ¼″ ID whose opening was locatedapproximately 10 cm from the surface of the mixing concrete, at a flowrate of 20 liters per minute (LPM) for 40-80 sec, for a total amount ofcarbon dioxide of 13.3 L (40 sec) to 26.7 L (80 sec). The remainingwater, 0.713 kg, was added to bring the mix to a w/c ratio of 0.6 whilethe concrete mix continued to be mixed after the carbon dioxide additionfor approximately 2 minutes, for a total mix time of approximately 4minutes, with carbon dioxide addition for 40, 60, or 80 sec during themixing. In general, the mixing procedure was as follows: mix dry mix andadd first water addition over 15 seconds; mix for remainder of oneminute; deliver CO₂ while mixing for 40, 60 or 80 seconds; when thedelivery was 40 seconds there was an additional 20 sec of post-CO₂mixing to bring the step up to one minute, when the delivery was 60 or80 seconds the next step began immediately after the CO₂ was stopped;add the second water addition and mix two minutes. In one test anadditional 5% water was added. These tests were done with Shaw prebagged mix, which required more water and was assumed to contain morecement (17%). The two water additions were 1.15 kg (58% giving 0.34estimated w/c) and 0.850 kg (to give a total of 2.0 kg of water andestimated 0.59 w/c). In the case of 5% added water it was only appliedon the second addition (1.150 kg or 55%, then 0.950 kg for a total of2.1 kg and estimated 0.62 w/c). Control concrete mixes were preparedwith the same final w/c ratio and mixing time, but no addition of carbondioxide. The mixed concrete was poured into cylinders and strength testswere performed at 7 days. The results are shown in FIGS. 4 and 5, wherethe bars represent the data range (high to low) and the point in themiddle corresponds to the average. The concrete mixes that had beenexposed to carbon dioxide showed 7-day strengths comparable to thecontrols.

In a second experiment, several batches were prepared. In each batch,approximately 20 kg of bagged readymix concrete (BOMIX bagged readymix)was mixed with water in a Hobart mixer. The cement content of theconcrete was not known but was assumed to be 20%. A first water additionof 0.6 kg (30% of total water) was added for a w/c ratio of 0.15 and themixer was topped with a loose lid. The concrete mix was mixed for atotal of 1 minute. Then a gas mixture containing carbon dioxide at aconcentration of 99.5% (Commercial grade carbon dioxide from AirLiquide, 99.5% CO2, UN1013, CAS:124-38-9) was delivered to contact thesurface of the mixing concrete via a tube of approximately ¼″ ID whoseopening was located approximately 10 cm from the surface of the mixingconcrete, at various flow rates for different batches, for 60 sec, togive different total carbon dioxide doses for different batches. Theremaining water of 1.4 kg was added to bring the mix to a w/c ratio of0.5 while the concrete mix continued to be mixed after the carbondioxide addition for approximately 2 minutes, for a total mix time ofapproximately 4 minutes, with carbon dioxide addition for 60 sec duringthe mixing (one minute premix, 60 sec CO₂ dose, then add remainder ofwater and finish with two minutes mixing for 4 minutes total). Controlconcrete mixes were prepared with the same final w/c ratio and mixingtime, but no addition of carbon dioxide. The mixed concrete was pouredinto 5 4 kg cylinders (100 mm diameter by 200 mm, or 4 inches by 8inches) and strength tests were performed at 7, 14, and 28 days. Thecarbon dioxide dosage is expressed on a per-cylinder basis, and was 5,10, 15, 20, 25, or 30 g per cylinder, depending on the batch, which was0.6, 1.3, 1.9, 2.5, 3.1, or 3.8% carbon dioxide bwc, respectively. Theresults are shown in FIGS. 6, 7, and 8. The concrete mixes that had beenexposed to carbon dioxide showed 7-day compressive strengths comparableto the controls, with a trend toward increasing 7-day strength withincreasing carbon dioxide dose (FIG. 6). 14-day compressive strengthswere comparable to or lower than controls at two doses, 15 and 20 g(FIG. 7). 28-day compressive strengths were comparable to the control,with a trend toward increasing 28-day strength with increasing carbondioxide dose (FIG. 8).

In a third experiment, additional water was added to compensate forreduced flowability (slump) observed in the concrete mixes contactedwith carbon dioxide in the previous experiments. Concrete mixes wereprepared as in the second experiment, except the dosages of carbondioxide used was 15 g per cylinder (1.9% carbon dioxide bwc). Inaddition, in one set of both control and carbon dioxide batches, thesecond water addition was increased to give a total water that was 4.7%increased over the default water addition 7-, 14-, and 28-daycompressive strength tests were conducted. The results are shown in FIG.9. Even with the additional water the concrete mix contacted with carbondioxide showed a 28-day strength comparable to control.

In a fourth experiment, various additional water amounts wereinvestigated. Concrete mixes were prepared as in the second experiment,except the dosages of carbon dioxide used was 10 or 15 g per cylinder(1.3 or 1.9% carbon dioxide bwc, respectively). In addition, in sets ofboth control and carbon dioxide batches, the second water addition wasincreased to give a total water that was 2100, 2200, 2300, 2400, or 2500ml/20 kg dry mix, compared to 2000 ml/kg for control batches. The amountof water on the first addition was 60% of the total water so the w/c attime of carbon dioxide was increased as mix water was increased. 7- and28-day compressive strength tests were conducted. The results are shownin FIGS. 10-13. Slump tests were also conducted and the results areshown in FIG. 14. Additional water partially compensated for thedecrease in slump with carbon dioxide addition, especially at the lowercarbon dioxide dose. 7 day strength was comparable to control for mostdoses of water.

Example 2

This example describes retrofitting an existing readymix truck with asystem for contacting a wet concrete mix in the drum of the truck withcarbon dioxide while the concrete mix is mixing.

A readymix concrete truck was retrofitted for delivery of carbon dioxideto the mixing concrete mix. A flexible rubber tube of approximately ¾″diameter was brought to the readymix site and the readymix truck wasretrofitted by running a flexible rubber tubing for delivery of carbondioxide in parallel with existing tubing for delivery of water to allowdelivery of carbon dioxide to the drum of the truck at the high end ofthe drum while a hydraulic cement mix, e.g., concrete, was mixing in thedrum. The opening of the tube was positioned 0.5 to 2 m from theconcrete in the truck. The truck was a six cubic meter transit mixer. Asource of carbon dioxide was attached to the flexible rubber tubing. Inthis example, the source of carbon dioxide was a liquid carbon dioxidesupply, heater (ethylene glycol), gas buffer tank, gas meteringequipment, and gas output, to supply carbon dioxide of at least 99%concentration. The gas delivery trailer took liquid carbon dioxide,metered by a pressure regulator and ran it through a heat exchangerwhere hot liquid glycol (antifreeze) heated it to change the liquidcarbon dioxide into a gas. The gas was stored in the receiver tanks on amobile cart which can be wheeled out of the trailer to a location insidethe plant. A touchscreen was used to program the correct dose of carbondioxide to be delivered during the concrete making process. Valves andsensors were used to meter the gas correctly. Hoses were used to connectbetween the trailer, cart and manifolds and the manifolds attach to theconcrete making machine to deliver the gas dose in the correct location.In industrial trials the gas line was ¾″ diameter.

In another readymix truck retrofit, the truck was retrofitted byconnecting the carbon dioxide source to the drum through the water linerelease. The water line went from the water tank on the truck to a Tjunction. Going up from the T sent the water into the drum. Going downfrom the T was a drain to empty the line onto the ground. The watersupply was turned off when not in use, essentially connecting the outletto the drum. By booking the gas supply into the outlet, in this example,the parallel line approach was avoided and it was only necessary to usea carbon dioxide supply and a conduit to connect to the T junction.

Example 3

This example describes the use of carbon dioxide to contact a mixingconcrete mix in a readymix truck.

The retrofitted readymix truck described in Example 2 was used. Thecomponents of a batch of concrete were added to the drum of the truck,including cement mix and aggregate. While the hydraulic cement mix wasmixing, carbon dioxide in a gaseous mixture that was at least 99% carbondioxide was introduced into the drum at a flow rate of 750, 1500, or2250 liters per minute for 180 seconds, for a total carbon dioxide doseof 0.5%, 1.0%, or 1.5% bwc, respectively. The drum remained open to theatmosphere during the carbon dioxide addition. After the flow of carbondioxide had stopped, additional water was added to the mixing concreteto bring the w/c ratio of the concrete to 0.45. The truck received theconcrete and the carbon dioxide at the batching bay, and delivered theconcrete to an adjacent building where testing was done and samples weremade. Tests were conducted for temperature, slump, and air content, andcylinders were made for strength and flexural strength.

In a second mixing example, carbon dioxide was added before anyadditional water was added to the mix, and the water in the mix duringcarbon dioxide addition was due to water in the aggregate mix, which hadbeen exposed to water before addition. The aggregate was wet and withthe addition of the wet aggregate the water content of the resultinghydraulic cement mix (concrete) was a w/c ratio of 0.17. Final mix waterwas achieved by adding water to the truck manually attain desiredconsistency.

Example 4

This example describes retrofitting a stationary pan mixer used to mixconcrete for use in a precast concrete operation with a system forcontacting the mixing concrete in the mixer with carbon dioxide. A gasline was attached to a carbon dioxide supply and run to a pan mixer formixing concrete for delivery to a mold. The line was configured to allowa controllable flow of carbon dioxide from the carbon dioxide to themixer for a predetermined time during mixing of the wet mix.

Example 5

This example describes the use of carbon dioxide to contact a mixingconcrete mix in a stationary pan mixer and pouring the concrete intomolds for precast concrete products. A retrofitted pan mixer asdescribed in Example 4 was used to deliver carbon dioxide to a wetconcrete mix in a mixer while the concrete was mixing, for 3 minutes, toobtain a dose of carbon dioxide of 0.5% to 2.5% bwc. The gas line wasabout 1 m from the concrete.

Example 6

This example describes the use of carbon dioxide to contact mixingconcrete mix in two different ready mix operations.

In a first operation, the following mix was used:

30 MPa with a maximum 4″ slump

-   -   20 mm aggregate—2780 kg    -   Sand—2412 kg    -   Washed sand—615 kg    -   Type 10 GU cement—906 kg    -   Fly ash—192 kg    -   Visco 2100-850 ml    -   ViscoFlow—1650 ml    -   Water—334 liters

The carbon dioxide was added via a ¾″ diameter rubber hose clipped tothe side of the truck and disposed in the mixing drum to deliver CO₂ tothe surface of the mixing concrete for 180 sec (controlled manually), atlow, medium or high dose, to achieve 0.43, 0.55, and 0.64% CO₂ bwc,respectively. Because the aggregate was wet, CO₂ was added to the mixbefore the final addition of water; the w/c of the mix when CO₂ wasadded was calculated to be 0.16. Final water was added immediately afterthe CO₂ addition.

The addition of CO₂ greatly reduced slump as time from arrival at siteprogressed, see FIG. 15. Carbonated concreted showed reduced strength at7 days compared to control, increasing in strength over time so that byday 56 the carbonated concrete was stronger than uncarbonated at alldoses tested. See FIG. 16. The addition of CO₂ caused an increase intemperature of the wet cement that was dose dependent, as shown in Table2.

TABLE 2 Effect of CO₂ dose on temperature, ready mix Mix Temperature (°C.) Control 15.2 0.43% CO₂ 17.0 0.55% CO₂ 18.4 0.64% CO₂ 19.4

Rapid chloride penetration tests (RCPT, using ASTM C1202 Standard TestMethod for Electrical Indication of Concrete's Ability to ResistChloride Ion Penetration) and flexural strength tests were alsoperformed. See FIG. 17. Although RCPT increased with carbonation (FIG.17A), since the control concrete was at the high end of low (generallyconsidered 1000 to 2000 coulombs) and the carbonated concrete was at thelow end of moderate (generally considered to be 2000 to 4000 coulombs)the difference was not considered to be significant. Flexural strengthdecreased slightly with carbonation (FIG. 17B).

In a second operation, mixes were prepared to meet a pre-determinedslump target of 5 inches, with additional water added to carbonatedbatches as necessary to achieve target slump. The following mix wasused:

-   -   Sand—770 kg/m³    -   20 mm Stone—1030 kg/m³    -   Cement GU—281 kg/m³    -   Fly Ash (F)—55 kg/m³    -   Water—165 L/m³    -   Daracem 50-1400 ml/m³    -   Darex II—200 ml/m³    -   Total—2301 kg    -   Water on CO₂ batches increased (unknown amount added after CO2        injection ends)    -   to achieve target slump.

CO₂ was introduced into the mixing drum of the ready mix truck via ahose connected at a T-junction to an existing water line that dischargedinto the mixing drum. As in the previous operation, because theaggregate was wet, CO₂ was added to the mix before the final addition ofwater; the w/c of the mix when CO₂ was added was calculated to be 0.16.Final water was added immediately after the CO₂ addition. Two doses ofCO₂ were used, 0.5% and 1.0% bwc, as well as an uncarbonated control.Additional water was added to the carbonated concrete to achieve targetslump. The concrete was used in a precast operation on site and arrived20-25 minutes after the mixing started.

The use of additional water brought the slump of the carbonated concreteto levels comparable to the uncarbonated control, as shown in Table 3:

TABLE 3 Slump, temperature, and air content of uncarbonated andcarbonated ready mix concretes Air Slump Temperature Mix Content (in) (°C.) Control 3.6% 5.5 23.9 0.5% 4.2% 4.5 26.2 CO₂ 1.0% 4.1% 5 28.6 CO₂

For the 0.5% carbonated concrete, two later slump measurements, at 20min and 35 min after arrival at the job site, were both 5 inches.Further measurements were not obtained for the 1.0% sample.

Compressive strengths of the batches are shown in FIG. 18. The 0.5% CO₂mix showed 85% strength compared to control at 1 day, equivalentstrength at 7 and 28 days, and 106% of control strength at 56 days. The1.0% CO₂ mix showed 71% strength compared to control, and 94% at 28 and56 days. The additional water added to achieve the target slump likelyreduced compressive strength of the concrete.

In a third operation, an admixture, sodium gluconate, was used torestore flowability. The following mix was used:

-   -   Sand—770 kg/m³    -   20 mm Stone—1030 kg/m³    -   Cement GU—336 kg/m³    -   Water—163 L/m³    -   Daracem 55-1350 ml/m³

CO₂ was introduced into the mixing drum of the ready mix truck via ahose connected at a T-junction to an existing water line that dischargedinto the mixing drum. As in the previous operation, because theaggregate was wet, CO₂ was added to the mix without a first wateraddition, and before the final addition of water; the w/c of the mixwhen CO₂ was added was calculated to be 0.16. Final water was addedimmediately after the CO₂ addition. Two doses of CO₂ were used, 1.0% and1.5% bwc, as well as an uncarbonated control. Sodium gluconate was addedto the 1.5% CO₂ batch at dose of 0.05% bwc, after the addition of CO₂.The concrete was used in a precast operation on site and arrived 20-25minutes after the mixing started.

The use of the sodium gluconate brought the slump of the 1.0% carbonatedconcrete toward levels comparable to the uncarbonated control, as shownin Table 4:

TABLE 4 Slump, temperature, and air content of uncarbonated andcarbonated ready mix concretes Air Slump Temperature Mix Content (in) (°C.) Control 5.9% 7 25.8 1.0% 5.9% 4 28.1 CO₂ 1.5% 4.5% 3 28.6 CO₂

For the 1.0% carbonated concrete (with sodium gluconate), a later slumpmeasurements, at 20 min after arrival at the job site, was 5.5 inches.For the 1.5% carbonated concrete (no sodium gluconate), a later slumpmeasurements, at 15 min after arrival at the job site, was 3.0 inches.Carbon dioxide uptake of the 1.0% dose was 0.44% bwc, for an efficiencyof 44%. Carbon dioxide of the 1.5% dose was 1.69% bwc, or 113%efficiency.

Compressive strengths of the batches are shown in FIG. 19. The 1.0%concrete (with sodium gluconate) had a compressive strength of 96, 107,and 103% of control at 1, 28, and 56 days, respectively. The 1.5%concrete (no sodium gluconate) had a compressive strength of 98, 117,and 109% of control at 1, 28, and 56 days, respectively. The 1.5% CO2concrete had a reduces slump but was still usable.

This example illustrates that carbonation can reduce slump in wet mixused in ready mix operations. Depending on the mix, the slump may besuch that remedial measures, such as use of additional water, use ofadmixture, or both, are necessary; as illustrated by this example, thesemeasures can restore slump to acceptable levels without major alterationin the strength of the concrete.

Example 7

This example describes the use of an admixture to modulatecompactability/strength of a dry cast concrete mix. Several differenttests were performed.

Work had identified that carbonation of fresh concrete prior toformation reduced the mass of an industrially produced carbonated drymix product in certain mixes. Dry mix products are made to a constantdimension so lower mass resulted in lower density which can contributeto lower strength. A lab investigation pursued novel admixtures toaddress the density issue. Sodium gluconate was studied in a labprogram. In conventional concrete sugars are known to be set retarders.The work investigated its use in conjunction with carbonated freshconcrete to see if the sodium gluconate would act in relation to thereaction products causing the density issue.

In a first test, the mix design was a dry mix concrete with thefollowing proportions

-   -   1.75 kg cement    -   15.05 kg SSD (saturated surface dry) fine aggregate    -   7.00 kg SSD (saturated surface dry) coarse aggregate    -   1.19 kg mix water    -   Target water was 6.05% by mass of the concrete

The admixtures used were: 1) Sodium gluconate to improve density—it wasprepared as a solution of 36.8 g of sodium gluconate per 100 ml ofwater. It was dosed into the concrete as a mass of solid sodiumgluconate by weight of cement; 2) Rainbloc 80—a water repellencyadmixture for Concrete Masonry Units; and 3) ProCast 150—an admixturefor use in concrete masonry units. The two commercial admixtures weredosed based upon mL/100 kg cementitious materials as per manufacturer'sspecifications.

Samples were mixed according to the following procedure:

-   -   Aggregate is introduced first and mixed until homogenous.    -   Cement is introduced and mixed for 30 s until homogenous.    -   Mix water is added over 15 seconds.    -   The concrete is mixed for a total of 4 minutes starting from the        water addition.    -   In the case of CO₂ batches the following modified sequence was        used:    -   1 minute mixing all materials    -   Initial temperature is recorded    -   CO₂ gas is injected over the surface of the mixing concrete at        100 LPM for required time based on test plan. The gas is        nominally retained in the bowl by use of a cover that        accommodates the movement of the mixing mechanism. The mixing        proceeds during the gas delivery.    -   Final temperature is recorded.    -   Admixtures are introduced to mix—always post carbonation    -   Mix for additional time to attain a total of 4 minutes mixing.

Concrete samples were formed according to the following procedure

-   -   Concrete was formed into standard 100 mm diameter cylinder molds    -   3.5 kg of dry mix materials were introduced into the molds and        compacted using a specially designed pneumatic ram which applies        95-100 psi of pressure directly under vibration onto the cross        section of the concrete mass    -   A steel trowel was used to remove any excess materials from the        top of the mold and level the surface of the test specimen.    -   The mass of the cylinder was recorded.    -   Test specimens were set to cure in a lime water bath, in        accordance with ASTM C192

The first trial produced four concretes: 1) Control; 2) Control with0.05% sodium gluconate; 3) CO2; 4) CO2 with 0.05% sodium gluconate. Thecylinder unit mass (mass of a constant volume of concrete) wasunderstood as an estimate of product density. 6 samples were produced.

With the control density as the standard, the control with sodiumgluconate had a relative density of 98.8%, the carbonated concrete was94.0% and the carbonated concrete with sodium gluconate was 93.4%. Thus,addition of 0.05% sg to control reduces cylinder density 1.2%,application of CO₂ reduces cylinder density 6%, and addition of 0.05% sgto CO₂ treated concrete did not improve cylinder density. The dose istoo low.

In a second trial, the same conditions for sample preparation as for thefirst trial were used, with the following carbonation and sodiumgluconate conditions:

-   -   Uncarbonated with 0, 0.24% and 0.48% sodium gluconate    -   CO₂ for 1 minute with 0.06%, 0.12%, 0.24% and 0.48% sodium        gluconate    -   CO₂ for 2 minutes with 0.10%, 0.24%, 0.48% and 0.72% sodium        gluconate

The effects of various doses of sodium gluconate on density, which canbe considered a proxy for strength, is shown in FIG. 20. Applying CO₂decreased the cylinder unit mass (proxy for density). Increasing theamount of CO₂ absorbed by the concrete correspondingly increased theamounts of sodium gluconate to offset the density shortcoming.Increasing the sodium gluconate dose increased the density of allconcretes over the range considered. The control concrete cylinder unitmass increased 1.7% at a dose of 0.48% sodium gluconate. For 1 min ofCO₂ the sodium gluconate dosages of 0.24% and 0.48% both resulted in acylinder mass equivalent to the control. For 2 minutes of CO₂ thecylinder mass was 99% of the control at a sodium gluconate dosage of0.48% and matched the control cylinder mass when the dose reached 0.72%.

In a third trial, the same conditions for sample preparation as for thefirst trial were used, with carbonation at 50 LPM for 90 seconds and thefollowing sodium gluconate conditions:

-   -   Control    -   CO₂ with 0.24% sodium gluconate    -   CO₂ with 0.30% sodium gluconate    -   CO₂ with 0.36% sodium gluconate    -   CO₂ with 0.42% sodium gluconate

Cylinder mass (density, assuming all cylinders are of equal volume) wasmeasured, and compressive strength measured at 1, 3, and 7 days.Cylinder densities are shown in FIG. 21. Applying CO₂ decreased thecylinder unit mass (proxy for density). Increasing the sodium gluconatedose increased the density over the range considered. The effectplateaued somewhat at the higher doses suggested the preferred dose ispotentially in the 0.30% to 0.42% range. Without gluconate the cylindermass of a carbonated product is about 7% less than the control. Agluconate dose of 0.30% brought the mass to 3% under the control. A doseof 0.42% brought the mass to 4% less than the control. The compressivestrengths of the sodium gluconate treated samples were comparable tothose of the control sample at doses of 0.30% and above.

In a fourth trial, the same conditions for sample preparation as for thefirst trial were used. Carbonation was at 50 LPM for 90 seconds and thefollowing sodium gluconate conditions:

-   -   Control    -   CO₂    -   CO₂ with 0.30% sodium gluconate    -   CO₂ with 0.42% sodium gluconate

All concretes contained Rainbloc (0.32%). It was added with the mixwater. The cylinder unit mass (mass of a constant volume) was measuredas a test of product density. 6 samples were produced. The strength wasmeasured at 1, 3 and 7 days. Cylinder densities are shown in FIG. 22.The application of CO₂ reduced the density (by 6%) and strength of theconcrete product The use of sodium gluconate improved the density andstrength. 0.3% sodium gluconate was sufficient to make carbonatedconcrete with 98.5% of the density of the control and equivalentstrength. 0.42% sodium gluconate produced carbonated concrete withequivalent density and strength to the control. The optimum dose forthis combination of cement and mix design proportions appears to be onthe order of 0.42% sodium gluconate by weight of cement.

In a fourth trial, the same conditions for sample preparation as for thefirst trial were used. Carbonation was at 50 LPM for 90 seconds and thefollowing sodium gluconate conditions:

-   -   Control    -   CO₂    -   CO₂ with 0.30% sodium gluconate    -   CO₂ with 0.42% sodium gluconate    -   CO₂ with 0.30% sodium gluconate with post-CO2 addition of        Procast.

In contrast to the previous days the cement was a 70/30 blend of whitecement and OPC. All batches contained Rainbloc (0.32%) and Procast 150(0.64%). The Rainbloc was added with the mix water while the Procast 150was tried both as part of the mix water and as an addition after thecarbon dioxide treatment. The strength was measured at 1 (2 samples),and 7 days (4 samples). Cylinder densities are shown in FIG. 23. Thecarbonation treatment produced a compacted concrete product that was 7%less dense than the control. The density was improved by adding sodiumgluconate. A dose of 0.30% sodium gluconate improved the density to 97%of the control. A further increase to 0.42% produced a concrete productwith a density of 96%. As compared to the earlier trial that did notinclude Procast, it is clear that the optimum dosage is sensitive to thepresence of other admixtures. Adding the Procast after the carbondioxide treatment provided improved product density. The timing of theaddition of admixtures with respect to the carbon dioxide application isimportant.

This example illustrates that an admixture, sodium gluconate, can returndensity and compressive strength of carbonated dry mix samples to thoseof uncarbonated samples, that the effect is dose-dependent, and that thetiming of delivery of additional admixtures added to the mix can affectstrength development.

Example 8

This example illustrates the effects of various admixtures on theworkability of carbonated mortar mix, prepared as for a wet castoperation.

A mortar mix was prepared containing 535 g Portland cement (Holcim GU),1350 g sand, and 267.5 g water. CO₂ gas was introduced at 20 LPM whilemixing. The time of CO₂ delivery depended on the target CO₂ uptake, forexample, to achieve 1.1% bwc the delivery took 3 to 4.5 min.

Three admixtures were used: sodium gluconate, fructose, sodiumglucoheptonate. The admixtures were added to carbonated mortar atdosages of 0.05, 0.10 and 0.20% by weight of cement. The dosages reflectsolid mass of additive delivered in a solution. The mortars werecarbonated while mixing to an uptake of about 1.9% by weight of cement.The admixture was added after the carbonation: after carbonation thetemperature of the sample was measured, then the admixture was added andthe sample was remixed to homogenize.

The slump of the produced mortar was measured as an assessment ofworkability. Slump was measure immediately after the end of mixing usinga Cement & Mortar Testing Equipments Transparence Acrylic Mini SlumpCone Test Apparatus (NL SCIENTIFIC INSTRUMENTS SDN. BHD. Malaysia.).Samples were rodded in two lifts.

Carbonation greatly decreased the mortar slump, while each of theadmixtures, added after carbonation, improved slump. The carbonatedslump matched the control upon addition of 0.05% fructose, 0.10% sodiumgluconate or 0.2% sodium glucoheptonate. See FIG. 24.

In a second test, mortar mixes were prepared and carbonated as above,and either fructose or sodium gluconate was added before (Pre), during(Mid), or after (Post) carbonation, and the CO₂ uptake as well as slumpwas measured in the mortar mix. It was seen that the addition ofadmixture either Pre or Mid carbonation did not appreciably correct thedecrease in slump caused by carbonation, whereas the addition ofadmixture Post carbonation greatly improved the slump (the apparentimprovement in slump in the sodium gluconate Pre sample can beattributed to the anomalously low carbon dioxide uptake of this sample);this was true for both sodium gluconate and fructose. See FIG. 25.

Example 9

This example illustrates the effect of the time of addition of admix onworkability and strength development in a carbonated mortar mix, as fora wet cast operation.

In a first test, mortar mix was prepared containing 535 g Portlandcement (Holcim GU), 1350 g sand, and 267.5 g water. CO₂ gas wasintroduced at 20 LPM while mixing. The time of CO₂ delivery depended onthe target CO₂ uptake, for example, to achieve 1.1% bwc the deliverytook 3 to 4.5 min. Mortar cubes were created with C109M-12 Standard TestMethod for Compressive Strength of Hydraulic Cement Mortars. All samplescontained 0.10% bwc PCE (Mighty 21ES by Kao Chemicals) to assist castingof cubes.

Sodium gluconate was added either before or after carbonation, at 0,0.025, 0.05, and 0.075% bwc. Compressive strength at 24 hours wasmeasured at 24 hours and compared to uncarbonated control. See FIG. 26.The sodium gluconate added after carbonation did not affect the 24-hourcompressive strength, whereas sodium gluconate added before carbonationimproved 24-hour compressive strength, but the mix was found to bestiff. The mix with sodium gluconate added after carbonation wasworkable, but strength development was adversely impacted.

In a second test, mortar was prepared and carbonated with or withoutsodium gluconate, added before or after carbonation, as in the firsttest, except the cement was Lehigh cement. The results were similar tothose for mortar prepared with Holcim cement: When added after CO₂ theadmix was a retarder and resulted in lower strengths at 24 hours. Whenadded before the CO₂ the retarding effect was not evident and 24 hstrength was ˜90% of control with relatively small SG dosages.

Example 10

This Example illustrates the effects of system temperature on carbondioxide uptake in a wet mix.

In a first test, an experiment was conducted to look at the effect ofthe initial temperature of the materials on the carbonation behavior offresh cement paste. Three target starting temperatures were considered,7° C., 15° C. and 25° C. (actual temperatures were ±2° C.). Measurementsinclude the mortar temperature, mini-slump (vertical slump and lateralspread), carbon dioxide uptake, and cube strength.

A mortar mix was prepared containing 535 g Portland cement (Holcim GU),1350 g sand, and 267.5 g water. The mix was brought to 7, 15, or 25° C.,and CO₂ gas was introduced at 20 LPM while mixing. The time of CO₂delivery depended on the target CO₂ uptake, for example, to achieve 1.1%bwc the delivery took 3 to 4.5 min. CO₂ uptake at various time pointswas measured. Slump measurements were also taken at various time points.

The effect of temperature on rate of carbon dioxide uptake is shown inFIG. 27, where the upper line and points are for 25° C., the middle lineand points are for 15° C., and the lower line and points are for 7° C.Rate of uptake of carbon dioxide increased as temperature increased; therate was 0.087% bwc/min at 7° C., 0.231 bwc/min at 15° C., and 0.331bwc/min at 25° C. The rate of carbon dioxide uptake increased 278% astemperature increased from 7 to 25° C.

The effect of temperature on slump is shown in FIG. 43. There was littleeffect on the workability with uptake of the mortar prepared at 7° C.(upper line and points). The workability of the mortar prepared at 15°C. declined rapidly with increasing uptake (lower line and points). Theworkability of the mortar prepared at 25° C. was between that of the twoother mortars declining with uptake but taking higher uptakes than the15° C. sample to reach zero workability (middle line and points).

In a second experiment, the effect of carbon dioxide temperature (heatedor unheated (cold) or form (dry ice), in some cases combined with theuse of ice water, on carbon dioxide uptake was measured in a cementpaste system. Cement, mix water (untreated or ice water) and admix weremixed for 30 seconds in blender, and initial properties and temperatureof the paste were evaluated. The paste was then carbonated while mixingin the blender. Carbonate while mixing in the blender, using heated gas,unheated gas (cold gas), or dry ice. Evaluate the final properties andtemperature of the paste. FIG. 28 shows the results of the study. Heatedor cold gases seemed to give approximately equivalent uptake. The mixeswith cold temperature (cold mix water, dry ice) did not give improvedcarbon dioxide uptake.

Example 11

This example illustrates the beneficial effect of calcium containingcompounds added before carbonation on 24 hour strength development in acarbonated mortar mix.

A mortar mix was prepared containing 535 g Portland cement (Holcim GU),1350 g sand, and 267.5 g water. CO₂ gas was introduced at 20 LPM whilemixing. The time of CO2 delivery depended on the target CO₂ uptake, forexample, to achieve 1.1% bwc the delivery took 3 to 4.5 min. Mortarcubes were created with C109M-12 Standard Test Method for CompressiveStrength of Hydraulic Cement Mortars. A plasticizer (0.10% MightyES+0.10% Sika VF) with or without Ca(OH)₂ (2.0% bwc) was added beforecarbonation, and effects on 24-hour compressive strength were measured.The results are shown in FIG. 29. Carbonation decreased the 24 hourstrength of the mortar. The use of a plasticizer improved the strengthof both carbonated and control mortars. The further addition of Ca(OH)₂decreased the 24 hour strength of the control product but furtherincreased the 24-hour strength of the carbonated product.

In a second experiment, CaO (1.5%), NaOH (2.2%), Ca(NO₂)₂, or CaCl₂(3.0%) were added before carbonation to a mortar mix as above. Resultsare shown in FIG. 30. All calcium compounds showed benefits for strengthdevelopment in the carbonated mortar mix, relative to carbonated mortarmix with no admixture added.

Example 12

This example illustrates that the timing of addition of an admixtureused for conventional purposes, in this case an air entrainer, relativeto carbonation, may be important to retain the effect of the admixture.

A calcium hydroxide slurry was used as a test system. 20 g of Ca(OH)₂was mixed with 40 g water to form a slurry. CO₂ gas was injected intothe slurry at 5 LPM. The temperature, an indicator of carbon dioxideuptake, was measured over a 9-minute period. The plain slurry containedno admixture, while the slurry with an air entrainer contained 2.5% (bymass of Ca(OH)₂ of a liquid solution of hydrocarbons used for airentrainment in concrete (AirEx-L, Euclid Chemical). The carbon contentwas quantified using a combustion infrared detection carbon analyzer(Eltra CS 800, Eltra GmbH, Germany). The net % CO₂ increase wascalculated in comparison to a base uncarbonated system containing thecomponents.

After 10 minutes of carbonation, the slurry without an additive showed aCO₂ uptake that was 25.5% of the original solid mass, while the slurrywith the air entrainer additive had an uptake that was 36.2%; thus, thesurfactant admixture increased the CO₂ uptake by 42.1%.

In a second test, various surfactants were tested for their effects onCO₂ uptake. Standard mortar mix, as in Example 8, was used, and thesurfactants were dosed at 0.10% bwc. CO₂ as injected for 6 minutesduring mixing. Initial and final temperatures were measured and netincrease in CO₂ content was measured as above. The results are shown inTable 5.

TABLE 5 Effects of surfactants on CO2 uptake Initial Final Net Temp,Temp, Temp CO₂ CO₂ Additive Source ° C. ° C. Change % increase None 23.833 9.2 1.65 Baseline Sunlight Dish soap 24.1 41.4 17.3 2.89 75% SunlightDish soap 24.1 41.9 17.8 3.34 102%  MB AE-90 BASF 23.4 33 9.6 1.80  9%Solar: w Guelph 23.8 35.2 11.4 2.17 31% Soap AirEX-L Euclid 23.8 40.616.8 2.84 72%

In a third test, mortar batches as above, containing 0.1% bwc of asurfactant air entrainer (Euclid AirEx-L), or no surfactant (control)were exposed to CO₂ during mixing for 0, 2, 4, or 6 minutes, and the CO₂uptake measured. There was greater uptake in the mortar treated with airentrainer than in control, untreated mortar at all time points, but therelative improvement was greater at the low exposure times: there was a117% increase in CO₂ uptake compared to control at 2 min, a 104%increase in CO₂ uptake at 4 minutes, and a 28% increase in CO₂ uptake at6 min.

In a fourth test, the effect of CO₂ addition before or after addition ofan air entrainer on mortar density was tested. A lower unit weightindicated a higher air content. Four air entrainers were used: EuclidAir-Ex-L, Grace Darex ii, BASF MB-AE 90, and Grace Darex AEA ED. Theresults are shown in FIG. 31. In all cases, addition of the airentrainer pre-CO₂ treatment led to an increase in density, whereasaddition of the air entrainer post-CO₂ treatment resulted in a densitythe same as untreated mortar.

This Example illustrates that the timing of CO₂ treatment relative toaddition an air entrainer affects rate of CO₂ uptake and density. If itis desired to maintain the density effect of the air entrainer, itshould be added after CO₂ addition. In some cases, a two-dose approachcould be used where an early dose of air entrainer is used to enhanceCO₂ uptake, then a later dose to achieve desired effects on density.

Example 13

This Example describes tests of carbonation in a precast dry mixoperation. Tests were conducted at a precast facility in which aconcrete mix was carbonated at different stages of the casting process,in some cases using a sodium gluconate admixture at variousconcentrations. The effects of carbonation, with and without admixture,on strength and water absorption were measured.

The concrete mix shown in Table 6 was used.

TABLE 6 Standard Block Design Component Name Amount Coarse aggregateBirdseye Gravel  685 lb Fine aggregate Meyers Mat Torp Sand 4320 lb Fineaggregate Silica Sand/Wedron 430 1250 lb Cement Illinois Product 1000 lbAdmixture Rainbloc 80  50 oz Target water content 6.5%

The aggregates, cement and water were added to a planetary mixer. Carbondioxide was flowed into the mixer via a ¾ inch diameter rubber pipe for180 s at a flow rate to achieve the desired carbonation. In some runs,carbon dioxide was added both at the mixer and at the feedbox. In apreliminary run, all water was added initially, but in subsequent runs,additional water was added about halfway through the 180 s according toan assessment of the mix consistency prior to the completion of the mixand additional water was added as necessary to achieve a desired mixlook. Batches with carbon dioxide delivered to the concrete requiredadditional water nearly in proportion to the amount of carbon dioxidegas supplied. The concrete mix was placed in a mold to produce 8 inchblocks, which were tested for density, compressive strength at 7, 28,and 56 days, and water absorption (all according to ASTM C140, 5 blocksper test). The carbonation of the concrete was also determined: Thesamples for analyzing the carbon dioxide content of the concrete werecreated by taking a fresh sample from the production line, drying theconcrete on a hot plate to remove the water, and subsequently sievingthe material through a 160 μm sieve. Samples of the raw materials wereexamined to determine how much of each component passes a 160 μm sieveand the carbon content of the passing material. This information, alongwith the concrete mix design, allows for the calculation of atheoretical control carbon content against which analyzed samples can becompared. The carbon content was quantified using a combustion infrareddetection carbon analyzer. The net % CO₂ increase was calculated incomparison to a base uncarbonated system containing the components.

In a first test, carbonation at both the feedbox and mixer or just thefeedbox was tested. The variations examined are summarized in TABLE 7,below. Data for controls, which were prepared on other days (samples 500and 700), are also presented.

TABLE 7 Standard Block Production Variables and Water Contents TotalDose Water Code Condition Mode (% bwc) w/c fraction 0600 ControlUncarbonated — 0.392 6.64% 0601 CO₂ Feedbox 0.5% 0.5% 0.422 8.32% 0602CO₂ Mixer 0.5% 0.5% 0.430 8.25% 0603 CO₂ Mixer 1.0% 1.0% 0.440 8.08%0604 CO₂ Mixer 1.0%, Feedbox 1.5% 0.450 8.23% 0.5% 0605 CO₂ Mixer 1.5%1.5% 0.455 8.39% 0500 Control Uncarbonated — 0.406 8.88% 0700 ControlUncarbonated — 0.426 7.45%

FIG. 32 shows the results of tests for carbon dioxide uptake,compressive strength, water absorption, and density for the blocksproduced in this test.

The efficiency of carbon dioxide uptake was greatest in the 1.5% bwcdose where carbon dioxide was delivered only to the mixer (batch 0605);delivery of 0.5% of the dose at the feedbox was consistently lessefficient than delivery of all of the same dose at the mixer (batch 0601compared to batch 0602; batch 0604 compared to batch 0605). A carbondioxide uptake efficiency of 93% was achieved with a CO₂ dose of 1.5%delivered solely at the mixer (batch 0605). Consequently, in subsequenttests a dose of 1.5% CO₂, delivered solely at the mixer, was used.

The addition of CO₂ to the mix consistently improved compressivestrength at 7, 28, and 56 days, at all doses tested, whether or not theCO₂ was added at the mixer, the feedbox, or both. The overall averagecompressive strengths of the two (uncarbonated) control sets (0500 and0700) were 2843, 3199, and 3671 psi at 7, 28, and 56 days, respectively.At 7 days the first four batches made with CO₂ (0601, 0602, 0603, and0604) showed a 30-36% strength benefit over the average control, and thefinal carbonated batch (0605) was 18% stronger. The strength benefit wasmaintained at 28 days with a benefit of the first four carbonatedconditions ranging from 29037% and the final batch being 19% better thanthe average control. The 56 day results indicated the strength benefithad increased to 30-45% for the first four sets and 36% for the finalset.

Water absorption was reduced through carbonation. Mixes 0601 to 0603 hada water absorption about 35% lower than that of uncarbonated control(0500 and 0700), and mixes 0604 and 0605, in which 1.5% CO₂ was added,had a water absorption of about 18% lower than control.

Density of the carbonated mixes varied with amount of carbon dioxideadded. The density of the two lowest CO₂ (0.5%) batches (0601 and 0602)was about 2.5% higher than control, but the density of the batchescarbonated at a dose of 1.0 or 1.5% (0603, 0604, and 0605) wereequivalent to the density of the control.

Overall, this test indicated that carbonation of this mixture in aprecast operation producing 8 inch blocks indicated that an efficiencyof carbon dioxide uptake of over 90% could be achieved, producing blocksthat were stronger than uncarbonated at all carbon dioxide doses andtime points tested, culminating in a 56 day strength that averaged over30% greater than control. Water absorption of the carbonated blocks wasconsistently lower than control, and the blocks carbonated at 1.0 and1.5% CO₂ dose had a density the equivalent of uncarbonated blocks.

In a second test, the mix of TABLE 8 was used, with a dose of 1.5% CO₂,delivered at the mixer, and, in addition five different doses of asodium gluconate admixture were delivered-0.1, 0.2, 0.3, 0.4, and 0.5%bwc. The sodium gluconate was delivered in water solution, dissolved onegallon of water (0.1, 0.2, and 0.3%) or in two gallons of water (0.4 and0.5%). The sodium gluconate admixture was added about 75 s after carbondioxide delivery to the mixer started, and took about 90 s to add.Admixture was added manually during the mixing cycle. The addition ofadmixture was begun during the carbon dioxide addition so as not toextend the mixing cycle. Carbonation, compressive strength, density, andwater absorption were measured.

The investigated variables and water contents are summarized in Table 8.The overall results are summarized in FIG. 32.

TABLE 8 Standard Block, with sodium gluconate CO₂ Dose Sodium Water CodeCondition Mode (% bwc) gluconate w/c fraction 0700 Control — — — 0.4257.35% 0701 CO₂ Mixer 1.5 0.5% 0.413 8.12% 0702 CO₂ Mixer 1.5 0.4% 0.4137.85% 0703 CO₂ Mixer 1.5 0.3% 0.424 7.99% 0704 CO₂ Mixer 1.5 0.2% 0.4267.87% 0705 CO₂ Mixer 1.5 0.1% 0.433 7.81% 0706 Control — — — 0.426 7.45%

The efficiency of CO₂ delivery for batches produced in this test wasfound to range from 78% to 94%, across all batches. The gas injectionparameters were held constant and the average efficiency was found to beabout 85%.

It was shown that the strength was sensitive to the admix dose. See FIG.33. The control strength can be taken at 100% at all ages and thecarbonated strengths are shown in relative comparison. For the lowerdoses the carbonated concrete strength was equivalent to the controlstrength at both 7 and 28 days. For a dose of 0.4% there was a 12%strength benefit at 7 days and equivalent performance at 28 and 56 days.For a dose of 0.5% there was a 34% strength benefit at 7 days, 28% at 28days, and 25% at 56 days. These results indicate that there is a certainamount of admixture required in the concrete beyond which a strengthbenefit can be realized.

It is shown that the water absorption was again reduced for thecarbonated products. All carbonated mixes were dosed with 1.5% CO₂ bwcand had similar uptakes. The water absorption was reduced 12% for thelowest and 31% for the highest admixture dose. The density showed somedependence on admixture dosage. The carbonation treatment with the smalldose of admixture decreased the density from 131 to 128.5 lb/ft³ (thoughit can be noted that the strength remained equivalent to the control).The density increased with admixture dose and equivalent density wasfound with a dose of 0.3% and density was 1.3% higher for the highestadmix dose.

Emissions Reduction:

The carbon dioxide absorbed in the concrete can effectively reduce theembodied carbon emissions. If the block mass and mix design are known,then the total emissions related to the cement can be determined. Inthis Example, the 17.7 kg block is found to be 12.9% (by wet mass)cement and thus there are 2282 g of cement in each block. The cement wassuggested by the supplier to be 94% clinker. If the emissions intensityof the clinker is assumed to be a generic 866 kg CO₂e/tonne of clinkerproduced then the clinker emissions for each block reach 1858 g. Ageneric carbonation uptake scenario can allow for an overall carbondioxide absorption and net emissions offset to be calculated. Theoverall uptake efficiency in the present Example, taking into accountall testing, was 88%. A 1.5% dose by weight of cement means that 34.2 gof CO₂ are dosed per block while the uptake efficiency means that 30.1 gare bound as stable carbonate reaction products in the block. Thedifference is a loss representing the 12% inefficiency. Under theseassumptions, the absorbed amount of carbon dioxide represents a directoffset of about 1.62% of the emissions from the clinker production. Anet sequestration consideration requires a detailed analysis includingthe emissions required to implement the technology. A reasonableestimate can be made by considering the energy to capture and compressthe CO₂ and the distance the CO₂ had to be transported. Additionalfactors are relevant (such as the creation and transport of the hardwarefor the technology) but are considered minor in the face of thegas-related aspects. The closest industrial CO₂ source to the trial sitewas 63 miles away. The transportation emissions can be taken to be 222 gCO₂/tonne-mile of freight (United States Environmental ProtectionAgency, 2014). The energy required to capture carbon dioxide is on theorder of 150 kWh/tonne. For 1000 blocks a 1.5% bwc dose would inject34,250 g of CO₂. The total absorption would be 30,140 g of CO₂. The gasprocessing and transport is calculated with respect to the totalinjected amount. The carbon dioxide emissions associated with the energyrequired to capture and compress the CO₂ is 3,522 g. The transportationof the liquid CO₂ 63 miles resulted in carbon dioxide emissions of 479g. No energy is required to vaporize the liquid CO₂ at the concreteplant if an atmospheric vaporizer is employed. The technology tocarbonate 1000 blocks would result in CO₂ emissions of 4,001 g. The netutilization, 26,139 g, is then the difference between the total carbondioxide absorbed and total process emissions. This means that 13.3% ofthe absorbed carbon dioxide cannot be associated with an environmentalbenefit due to the associated emissions. However, it suggests that thenet efficacy of the CO₂ utilization is 86.7%. A sensitivity analysis cansuggest how location-specific inputs can affect the sequestrationefficacy. Certain locations are further from sources of industrial CO₂than the present case. If the liquid CO₂ transport distance wasincreased to 600 miles (reasonable in markets where industrial gases areshipped from distant areas) then the increase in transport emissionsreduces the estimated efficacy to 73.2%. However, if the distance waskept at 63 miles then the effect of grid emissions on carbon dioxideprocessing emissions can be examined. An example of low grid emissionscan be found in New York where parts of the state see 548.37 lb CO₂e/MWh(248.7 g CO2e/kWh). The reduced gas processing emissions would increasethe sequestration efficacy to 94.2%. An example of very low gridemissions can be found in Quebec at 5.1 lb CO₂e/MWh (2.3 g CO₂e/kWh),where the efficacy would reach 98.4%. On the other hand, Colorado hashigh grid emissions of 1906.27 lb CO₂e/MWh (864.7 g CO₂e/kWh). Theefficacy would decrease to 83.7%. These estimates are consistent with apreviously examined case. On the order of 80-90% of the carbon dioxideabsorbed by the concrete would represent a net removal of CO₂ from theatmosphere while the balance would be offset by the emissions requiredto employ the technology.

This example illustrates that carbon dioxide can be added to a precastconcrete mix in a dry cast operation at the mixer stage and the productsformed are generally stronger, show lower water absorption, andequivalent density when compared to non-carbonated products. Theaddition of a sodium gluconate admixture resulted in a dose-dependenteffect on strength, water absorption and density, and indicated that anoptimum dose for admixture can be achieved to optimize these parameters.

Example 14

In this example the same precast equipment was used in the same facilityas in Example 13, but using three different concrete mixes: a limestonemix, a lightweight mix, and a sandstone mix. This example illustratesthe importance of adjusting carbonation mix parameters to mixes withdifferent characteristics.

Three different mix designs were used, shown in TABLES 9, 10, and 11.

TABLE 9 Limestone Block Mix Design Component Name Amount Coarseaggregate Sycamore FA-5 3152 lb Coarse aggregate Sycamore FM-20 5145 lbFine aggregate Silica Sand/Wedron 430 745 lb Cement Illinois Product 351lb Cement White Cement 819 lb Admixture Rainbloc 80 59 oz AdmixtureFrocast 150 117 oz Target water content 8.6%

TABLE 10 Lightweight Block Mix Design Component Name Amount Coarseaggregate Birdseye Gravel 1030 lb Coarse aggregate Gravelite 1500 lbFine aggregate Screening Sand 2200 lb Fine aggregate Meyers Mat TorpSand 1500 lb Cement Illinois Product  725 lb Admixture Rainbloc 80  34oz Target water content 7.9%

TABLE 11 Sandstone Block Mix Design Component Name Amount Coarseaggregate Sycamore FA-20 3750 lb Fine aggregate Meyers Mat Torp Sand1800 lb Cement Illinois Product  730 lb Admixture Rainbloc 80  37 ozTarget water content 7.0%

Limestone Mix Test.

In a first test, the limestone mix of TABLE 9 was used. Conditions wereas for the second test of Example 13, with CO₂ added at a dose of 1.5%in the mixer. Addition of 0.4% sodium gluconate was tested. The additionof the Procast admixture that is normally part of the mixing sequencefor the limestone mix design was delayed to be added after the carbondioxide injection was complete. The investigated variables and watercontents are summarized in Table 12. The overall results are summarizedin FIG. 34.

TABLE 12 Limestone Mix Production Variables and Water Contents CO₂ DoseWater Code Mix Design Condition Mode (% bwc) Admix w/c fraction 0805Limestone Control — — — 0.225 7.75% 0806 Limestone CO₂ Mixer 1.5 0.4%0.514 8.53%

The limestone mix design was examined in only a limited production runpartly due to the perceived difficulty of accurately assessing the netamount of absorbed carbon dioxide against the high carbon content of thelimestone background, at least when using the current analytical methodsand procedures.

The compressive strength data showed that the carbonated limestoneblocks averaged 2349 psi at 7 days and were slightly weaker (7%) thanthe control blocks. The 28 day strength was 2518 psi and 14% lower thanthe control. The 56 day strength averaged 2762 psi and 9% weaker thanthe control though this gap could be narrowed to 6% if an outlier pointwas removed. The dose of admixture in this test was determined using theIllinois Product cement and no advance tests on the Federal White cementused in the limestone mix design were performed. Subsequent labdevelopment has made it clear that the effect and dosage of theadmixture is sensitive to cement type. The integration of thecarbonation technology may require a small investigative series of trialruns to determine both if the admixture is desired and what the properdose should be. The success at demonstrating the admixture usage, forthe Illinois Product cement, in the lab prior to the pilot suggests thatpreliminary optimization screening could be accomplished for any mix forwhich the materials were available.

In terms of water absorption, it was found that the carbonated limestoneblock had a higher absorption and lower density than the control blocks.The absorption was increased 18% and the density was decreased 2%. Theresults agree with the lower strength of the carbonated limestone blocksand support the need to fine tune the inputs used when carbonating thismix.

Lightweight Mix Test.

In a second test, the lightweight mix of Table 10 was used. Conditionswere as for the second test of Example 13, with CO₂ added at a dose of1.5% in the mixer. Addition of sodium gluconate at three differentlevels, 0.35, 0.4, and 0.45% was tested. The investigated variables andwater contents are summarized in Table 13. The overall results aresummarized in FIG. 35.

TABLE 13 Lightweight Mix Design Production Variables and Water ContentsCO₂ Dose Water Code Mix Design Condition Mode (% bwc) Admix w/c fraction0801 Lightweight Control — — — 0.745 6.96% 0901 Lightweight CO₂ Mixer1.5 — 0.691 12.25% 0902 Lightweight CO₂ Mixer 1.5 0.35% 0.703 13.79%0802 Lightweight CO₂ Mixer 1.5 0.40% 0.758 8.80% 0903 Lightweight CO₂Mixer 1.5 0.45% 0.707 13.99%

Preliminary results suggest that an increase in CO₂ content similar towhat has been observed for the Standard Block occurred for carbonatedLightweight mixes in all cases. However, due to inherent difficultiesperforming carbon quantification for these mix designs a definitiveanalysis was not performed, and actual numbers obtained, in some casesover 100%, are not reliable.

The compressive strength data for the lightweight mix is summarized inFIG. 36. The testing broke three blocks from the control set and fiveblocks from each of the carbonated sets. The control (uncarbonated, nosodium gluconate) strength can be taken at 100% at all ages and thecarbonated (with and without sodium gluconate) strengths are shown inrelative comparison. The carbonated batch with no sodium gluconate wasslightly behind the control at 7 days but developed strength at a fasterrate thereafter. The admixture batches were found to be stronger at thefirst measurement and maintained at least this level or benefit throughthe remainder of the test program.

The lightweight block production found an optimal or near-optimal amountof admixture. With no admixture used the strength was 11% behind thecontrol strength at 7 days, 5% ahead at 28 days and 10% ahead at 56days. The carbonated concrete with low admixture dose was 22%, 42% and41% stronger than the uncarbonated control at 7, 28 and 56 daysrespectively. The 0.40% dose produced concrete that was 76%, 94% and 84%stronger at the three ages while the 0.45% dose of admixture resulted in21%, 32% and 33% improvements. These results are different than thosefor Standard Block in Example 13, where an optimal dose of sodiumgluconate was not necessarily reached even at 0.5%, and illustrates theusefulness of pre-testing, or otherwise optimizing, admixture dose andother conditions specific to a specific mix design. See Example 15 for afurther testing of this.

CO₂ injection had little effect on the lightweight block density orwater absorption when no sodium gluconate was used. Across the dosagesof admixture the water absorptions were decreased about 10% for the0.35% and 0.45% doses and 34% for the middle dose of 0.4%, compared touncarbonated control without sodium gluconate. Conversely, the densityincreased when sodium gluconate was used. It was up 1-2% for high andlow doses and 7% higher for the middle dose, compared to uncarbonatedcontrol without sodium gluconate. While the middle dose carbonatedblocks were the strongest and had the lowest water absorption they werealso the highest density. Promising strength and absorption results werefound with the other two admixture dosages and accompanied by a smalldensity increase. Admixture usage will generally benefit frompre-testing or other predictive work to optimize conditions to obtainthe desired result, e.g., in the case of lightweight blocks, acombination of strength, density, water absorption, and other propertiesas desired.

Sandstone Mix Test.

In a third test, the sandstone mix of Table 11 was used. Conditions wereas for the second test of Example 13, with CO₂ added at a dose of 1.5%in the mixture Addition of 0.35, 0.4, and 0.45% sodium gluconate wastested. The investigated variables and water contents are summarized inTable 14. The overall results are summarized in FIG. 37.

TABLE 14 Sandstone Mix Design Production Variables and Water ContentsCO₂ Dose Water Code Mix Design Condition Mode (% bwc) Admix w/c fraction0803 Sandstone Control — — — 0.672 6.55% 0904 Sandstone CO₂ Mixer 1.5 —0.697 6.93% 0905 Sandstone CO₂ Mixer 1.5 0.35% 0.736 7.00% 0804Sandstone CO₂ Mixer 1.5 0.40% 0.710 7.29% 0906 Sandstone CO₂ Mixer 1.50.45% 0.718 7.02%

Preliminary analysis of the Sandstone samples found CO₂ contents to behigher in all carbonated mixes relative to the control. The averageefficiency of CO₂ delivery for batches produced was found to range from20% to 90% at a 1.5% by weight of cement CO₂ dose. From the preliminaryanalysis batch 0905 appears to contain a smaller amount of captured CO₂compared to other batches produced under similar conditions. Furtheranalysis is currently underway to confirm this result. The averageefficiency of CO₂ delivery considering all Sandstone batches isapproximately 66%, however rises to approximately 81% if batch 0905 isomitted from the calculation.

The compressive strength data for the sandstone mix is summarized inFIG. 38. The testing broke three control blocks and five carbonatedblocks. The data is plotted to show every individual break with theaverage compressive strength highlighted. The sandstone carbonatedblocks with no admixture had a strength that was functionally equivalentto the control (carbonated, no admixture) strength (4% behind at 7 days,2% ahead at 28 days and 5% behind at 56 days). Of three doses ofadmixture, strength increased with admixture dosage suggesting that thedosage was reaching an optimum across the range considered. The 7 daystrength benefit was 7%, 9% and 63% on the three admixture dosagesconsidered. The benefit at 28 days was 8%, 22% and 63% respectively. At56 days was 9%, 8% and 58% respectively. The strength increase withadmixture dose across the range of dosages mirrors the data with theStandard Block of Example 13 wherein some “threshold” amount of admixseems to be crossed in relation to the amount of carbon dioxide presentin the concrete.

The carbonation treatment without using the admixture increased thewater absorption 12% and decreased the density 3%. The use of admixturebrought the metrics back in line with the control at the lowest dose andoffered significant improvement at the highest dose. The waterabsorption was reduced 19% and the density was increased 3% for thecarbonated blocks with 0.45% dose of the admixture. As with other mixes,the final desired properties of the blocks will determine whetheradmixture, such as sodium gluconate, is used, and under what conditions,e.g., at what concentration, which can be pre-determined by preliminarytesting or by other appropriate test.

This example illustrates the importance of tailoring carbonationconditions, e.g., admixture usage, to the exact mix design beingconsidered, in that the three mixes used showed differing responses tosodium gluconate as an admixture, and also had different requirements.For example, in the lightweight mix, density is an importantconsideration and may dictate that a lower dose of admixture be usedthan that that produces maximum strength development and/or minimumwater absorption. For other mixes, other considerations may play adominant role in determining carbonation conditions, such as use ofadmixture.

Example 15

This example illustrates the use of a sodium gluconate admixture with amedium weight mix design, where the admixture dose was pre-determinedbased on results from the batches tested in Examples 13 and 14.

A Medium Weight mix design was used at the same facility and with thesame equipment as in Examples 13 and 14. The mix design is given inTable 15.

TABLE 15 Medium Weight Mix Design (target w/c = 0.78) Ingredient AmountFraction Birdseye Gravel 1030 lbs 12.8% Illinois Product Cement  675 lbs8.4% McCook Block Sand 1800 lbs 22.3% Meyers Torp Sand 2270 lbs 28.1%Screening 2300 lbs 28.5% RainBloc 80  34 z —

It was found that the best dose of sodium gluconate in the Standard,Lightweight, and Sandstone mixes used in Examples 13 and 14 was linearlyrelated to cement content. See FIG. 39. Based on this relationship, andadjusted for the fact that the CO₂ dose was to be 1.0% rather than 1.5%used in the Standard, Lightweight, and Sandstone, a sodium gluconatedose of 0.25% bwc was used. Blocks were produced as described in Example13, with uncarbonated−sodium gluconate (control), uncarbonated+sodiumgluconate, carbonated−sodium gluconate, and carbonated+sodium gluconate,and tested for compressive strength and density. The blocks were alsosubmitted for third party testing which also included water absorption(Nelson Testing Laboratories, Schaumberg, Ill.).

Compressive strength and mass results for 7, 28, and 56 days aresummarized in FIG. 40. The direction of the arrows represents time ofmeasurement, from 7 to 56 days. The uncarbonated blocks with sodiumgluconate were slightly denser and stronger than uncarbonated blockswithout sodium gluconate at all time points tested, while the carbonatedblocks without sodium gluconate were lower in strength and mass thanuncarbonated without sodium gluconate, and the carbonated with sodiumgluconate were both stronger and lighter than the uncarbonated withoutsodium gluconate.

The results of third party testing are shown in FIG. 41. Three blockdata sets were used, with all batches meeting ASTM C90 specification.CO₂ alone made the blocks 6% weaker than control, but using CO₂ plussodium gluconate made it 8% stronger than control. CO₂ alone increasedwater absorption by 7% compared to control, but CO₂ plus sodiumgluconate resulted in blocks with 4% lower water absorption compared tocontrol. Shrinkage was increased for both CO₂ and CO₂ plus gluconatesets, but for the sodium gluconate batch it was effectively equivalentto the control.

This example demonstrates that a pre-determined sodium gluconate dosefor a new mix, based on previous results, was sufficient to producecarbonated blocks comparable in mass and shrinkage, greater incompressive strength, and lower in water absorption than uncarbonatedblocks without sodium gluconate.

Example 16

The following protocols were used in EXAMPLES 17 to 21, withmodifications as indicated in particular examples.

Mortar Mix

-   -   1. Prepare the mixing bowl by dampening the sides with a wet        cloth, be sure to remove any pooling water from the bowl before        introducing raw materials.    -   2. Weigh the necessary amount of water for your test and add the        water to the damp, empty mixing bowl.    -   3. Add sand to mixer    -   4. Blend sand and water for 30 seconds on Speed #2    -   5. Scrape the sides of the bowl with pre wet rubber spatula to        remove any materials sticking to the sides of the mixing bowl    -   6. Add the required cementitious materials to the mixing bowl    -   7. Blend Sand, water and cementitious materials for 30 seconds        at Speed #2    -   8. Record the time that cementitious materials are added to the        mix    -   9. Scrape the sides of the mixing bowl with a pre wet rubber        spatula    -   10. Record the temperature    -   11. If you are not carbonating, skip to step 14    -   12. Carbonate at a flow rate of 20 liters per min for desired        duration.    -   13. Record final temperature    -   14. Scrape the sides of the bowl with pre wet rubber spatula    -   15. Introduce necessary admixtures—the mixing sequence and        dosing details of the admixtures and additives may vary        according to test. Record time and dosage.    -   16. After each admixture or sugar is added, blend for 30 seconds    -   17. Measure slump using the Japanese slump cone. Record slump        and spread (two measurements).    -   18. For slump retention, return to bowl, wait, remix 30 sec        before next slump.    -   19. Produce a sample for calorimetry    -   20. Fill three mortar cubes molds with mortar (Procedure ASTM        C109/C109M−12 Standard Test Method for Compressive Strength of        Hydraulic Cement Mortars)    -   21. Cover mortar cubes with a plastic garbage bag or damp cloth        and demold only after 18+/−8 hours have passed    -   22. Break cubes at 24 hours+/−30 minutes (use time that cement        was introduced into the mix as an indicator of when samples        should be broken)

Concrete Mix

-   -   Wet inside mixer, add all stone and sand, mix 30 seconds to        homogenize    -   Add all cementitious materials, mix one minute to homogenize    -   Add all batch water over a period of 30 seconds, mix all        materials for one minute    -   Take initial temperature    -   Control batch—mix for 4 minutes and take final temperature. Add        admixtures as required, mix one minute    -   Carbonated mix—inject CO₂ gas at 80 LPM, enclose mixer, mix        while carbonating for required time    -   Remove cover and record final temperature, Add admixtures as        required, mix one minute    -   Record slump (ASTM C143) and cast 6 compressive strength        cylinders (ASTM C192)    -   Take two samples for moisture/carbon quantification bake off,        one sample for calorimetry    -   Demould cylinders after 28+/−8 hours and place them in a lime        water bath curing tank at a temperature of 23° C.+/−3° C.    -   Test compressive strength 24 hours (3 samples) and 2 at 7 days        (2 samples)

Example 17

In this example the carbon dioxide uptake of cements from two differentsources, Lehigh and Holcim, were compared.

Mortar mix made under a 20 LPM flow of CO₂ gas. Samples were removedfrom the batch of mortar every 60 s until the 8 minute point. The carbondioxide content was measured and a curve constructed relating the lengthof exposure to CO₂ gas to the approximate amount of CO₂ uptake. Twocements were compared. Mix design was 1350 g EN sand, 535 g of cement,267.5 g of water. w/c=0.5.

The results are shown in FIG. 42. Carbon dioxide uptake increased withtime, as expected, but the rate of increase was different for the twodifferent cements. At a w/c of 0.5, the mortar paste can absorb carbondioxide but to exceed 1% uptake would take 3 to 5 minutes, depending onthe cement type used.

This Example illustrates that a w/c of 0.5 allows carbon dioxide uptake,but at a rate that may not be compatible with mix times in somesettings, and that the source of the cement can affect the properties ofa hydraulic cement mix made with the cement regarding carbon dioxideuptake.

Example 18

In this Example, the effect of w/c ratio on carbon dioxide uptake wasstudied.

In a first study, a test performed with mortar. The total mix was 990 gof Ottawa sand, 440 g cement, with 206 g of total water. Water, sand andcement were mixed, with the water added in two stages. CO₂ was suppliedfor various times at 10 LPM after the first water addition, whichbrought the mix to either 0.1 or 0.45 w/c, and the remaining water wasthen added and mixing completed. Carbon uptake at various time pointswas measured, as shown in FIG. 44. The rate of carbon dioxide uptake washigher for the paste with w/c 0.1 at time of reaction than for w/c of0.45.

In a second study, a series of tests were performed on mortar. Mortarmix made under a 20 LPM flow of CO₂ gas. The carbon dioxide content wasmeasured and a curve constructed relating the w/c of the mortar mix atthe time of carbon dioxide addition to the approximate amount of CO₂uptake. Mix design was 1350 g EN sand, 535 g of cement (Holcim GU),267.5 g of water. Total w/c=0.5 Water was added in two stages. Oneportion before carbonation, the remaining portion after 1 min ofcarbonation. The amount before carbonation ranged from 10% to 100% oftotal (w/c=0.05 to 0.50). The effect of w/c on carbonation at 1 minuteis shown in FIG. 45 and Table 16.

TABLE 16 Effect of w/c in mortar on carbon dioxide uptake Relative toinitial w/c Uptake 0.05 level 0.50 0.00 0.05 1.98 100% 0.10 1.56 79%0.15 1.52 77% 0.20 1.29 65% 0.25 1.32 67% 0.30 1.24 63% 0.35 0.77 39%0.40 0.78 40% 0.45 0.48 24% 0.50 0.35 18%

Drier mortar systems showed higher rates of uptake than did wet systems.1.98% uptake at 0.05 w/c declined to 0.35% at 0.50 w/c.

In a third test, a trial concrete mix was prepared with split wateradditions. The total mix was 300 kg/m³ cement, 60 fly ash, 160 water,1030 stone, 832 sand. The water was added in two stages. CO₂ suppliedfor 180 seconds at 80 LPM after the first water addition. Remainingwater then added and mixing completed. The w/c at carbon dioxideaddition was 0.1, 0.15, or 0.45. The results are shown in FIG. 46. Aswith mortars, the carbon uptake increased with lower w/c when the carbondioxide is delivered.

Example 19

This example illustrates that temperature rise during carbonation of ahydraulic cement mix is highly correlated with degree of carbonation andcan be used as an indicator of degree of carbonation in a specificsystem.

In a first test, the mortar used in the second test of Example 17 alsohad temperature measurements taken at the various time points. Theresults are shown in FIG. 47. There was a linear relationship betweendegree of carbonation and temperature increase in this system, in whichw/c was varied and carbon dioxide exposure was kept constant.

In a second test, temperature vs. carbon dioxide uptake was studied inmortars prepared with three different cements, Holcim GU, LafargeQuebec, and Lehigh. Mortar was prepared at a w/c=0.5 and carbonated forvarious times at 20 LPM CO2. The results are shown in FIG. 48. There wasalso a linear relationship between degree of carbonation and temperaturerise in this system, in which w/c was kept constant at 0.5 and time ofcarbon dioxide exposure was varied. The relationship was relativelyconstant over different cement types. The slopes of the line differ inthe two tests, which were conducted in two different systems, reflectingthe specificity of temperature rise with carbonation to a particularsystem.

These results indicate that in a well-characterized system, temperatureincrease may be used as a proxy indicator for carbon dioxide uptake.

Example 20

This example illustrates the effects of different admixtures on slumpand compressive strength in concrete.

In a first test, sodium gluconate at 0, 0.1% or 0.2% was added to aconcrete mix after carbonation and the effects slump at 1, 10 and 20minutes after mixing were measured, and compared to control,uncarbonated concrete. The results are shown in FIG. 49 and Table 17.The slump of the carbonated concrete is less than half of the control at1 min and declines to no slump at 10 min. Adding 0.1% sodium gluconateafter carbonation gave a slump equal to the control at 1 min, 80% at 10min and 50% at 20 min. Adding 0.2% also provided high slump than thelower dose at all intervals, before being 75% of the control at 20 min.

TABLE 17 Effects of sodium gluconate on concrete slump Control CO₂Control SG - 0.1% SG - 0.2%  1 min 100% 46% 100% 108% 10 min 100% 0% 80%140% 20 min 100% 0% 50% 75%

In a second test, the effects of fructose at various concentrations oninitial slump of a concrete mix were tested. Fructose was added aftercarbonation. Total mix was 4.22 kg cement, 1 kg fly ash, 3.11 kg water,16.96 kg stone, 14.21 kg sand. The results are shown in FIG. 50.Carbonation reduced the slump of the concrete. In response, fructose wasadded after carbonation is proportions of 0.05, 0.10 and 0.20% by weightof cement. The dosages reflect solid mass of additive delivered in asolution. The CO₂ content was quantified as 1.3%, 1.4% and 1.5% byweight of cement for the three carbonated batches respectively. 0.20%fructose was sufficient to restore the slump to be equivalent to thecontrol. However, fructose had a strength retarding effect, as shown inFIG. 51. Strength at 24 hours was significantly less than uncarbonatedcontrol, but strengths at 7 days was acceptable, with higher strengthsassociated with higher fructose contents.

Example 21

In this example, a variety of different cements were tested in a mortarmix to determine variations in response to carbonation.

Six cements were tested: Holcim GU (Hol), Lafarge Quebec (LQc), LafargeBrookfield (LBr), Lehigh (Leh), Illinois Product (Ipr), and NorthfieldFed White (NWh). The properties and chemistries of the different cementsare given in Table 18.

TABLE 18 Properties and chemistries of different cements Metric Hol LQcLBr Leh IPr NWh Surface Area - 423 417 392 425 501 408 Blaine (m²/kg)Free CaO (%) 0.31 0.94 0.16 1.45 1.45 1.47 CaO (%) 62.22 60.56 62.6861.55 62.61 65.36 Na₂Oe (%) 0.28 0.38 0.18 0.11 0.41 0.08 SiO₂ (%) 20.3019.18 20.10 19.53 19.12 21.41 Al₂O₃ (%) 4.62 4.72 5.24 4.45 5.47 4.38TiO₂ (%) 0.22 0.21 0.26 0.32 0.29 0.08 P₂O₅ (%) 0.14 0.26 0.05 0.25 0.130.01 Fe₂O₃ (%) 2.50 2.74 2.27 3.00 2.23 0.20 MgO (%) 2.21 2.80 1.48 3.212.70 0.90 Na₂O (%) 0.22 0.32 0.11 0.06 0.34 0.06 K₂O (%) 0.92 0.84 1.090.70 1.01 0.28 Mn₂O₃ (%) 0.05 0.09 0.07 0.18 0.19 0.01 SrO (%) 0.08 0.240.06 0.04 0.07 0.03 SO₃ (%) 3.63 3.79 4.10 2.96 3.88 3.94 BaO (%) 0.060.05 0.13 0.05 0.05 0.08 ZnO (%) 0.04 0.07 0.00 0.02 0.01 0.00 Cr₂O₃ (%)0.01 0.03 0.01 0.01 0.01 0.00 Loss on 2.52 4.08 2.38 3.54 1.98 3.00ignition to 975° C. (%)

The mortar mix was EN 196 Sand 1350 g, Cement 535 g, Water 267.5 g, w/cRatio 0.5. CO₂ was added to the mixing bowl at 20 LPM for durations of0, 2, 4, 6, and 8 minutes. Temperature change, slump, flow-spread, CO₂uptake, and 24 hr cube strength were measured. The results are given inTable 19.

TABLE 19 Properties of carbonated mortars made with different cementsHol LQc LBr Leh IPr NWh 0 min CO₂ CO₂ Uptake (% bwc) 0.00 0.00 0.00 0.000.00 0.00 Delta T (° C.) 0.0 1.1 1.2 0.7 1.3 1.0 Slump (mm) 110 115 100110 95 105 Slump (% of Control) 100%  100%  100%  100%  100%  100%  Work(mm) 157 185 144 165 130 180 Strength (MPa) 20.2 15.0 25.1 16.0 33.420.4 Strength (% of Control) 100%  100%  100%  100%  100%  100%  2 minCO₂ CO₂ Uptake (% bwc) 0.87 0.64 0.47 0.67 0.55 0.69 Delta T (° C.) 2.93.6 2.8 4.3 3.7 6.5 Slump (mm) 70 105 40 50 10 30 Slump (% of Control)64% 91% 40% 45% 11% 29% Work (mm) 83 140 58 60 10 35 Strength (Mpa) 9.97.6 12.0 13.1 31.3 17.3 Strength (% of Control) 49% 38% 48% 65% 94% 85%4 min CO₂ CO₂ Uptake (% bwc) 0.94 0.88 1.10 1.30 1.79 0.88 Delta T (°C.) 4.9 6.1 7.6 7.2 9.3 9.3 Slump (mm) 60 70 20 45 0 8 Slump (% ofControl) 55% 61% 20% 41%  0%  8% Work (mm) 75 78 21 45 0 10 Strength(MPa) 9.9 8.1 11.2 10.9 27.5 16.4 Strength (% of Control) 49% 40% 45%54% 82% 80% 6 min CO₂ CO₂ Uptake (% bwc) 1.96 1.74 4.06 1.84 2.71 1.57Delta T (° C.) 7.6 9.2 9.7 11.2 13.2 12.7 Slump (mm) 35 70 0 35 0 0Slump (% of Control) 32% 61%  0% 32%  0%  0% Work (mm) 35 89 −6 37 0 0Strength (MPa) 8.8 6.4 11.2 13.4 29.5 — Strength (% of Control) 43% 32%45% 66% 88% — 8 min CO₂ CO₂ Uptake (% bwc) 2.76 1.68 1.27 2.23 3.75 2.07Delta T (° C.) 13.4 9.2 14.8 14.7 22.2 17.3 Slump (mm) 5 40 0 15 0 0Slump (% of Control)  5% 35%  0% 14%  0%  0% Work (mm) 5 44 −8 13 0 0Strength (MPa) 8.2 6.8 13.9 14.5 — — Strength (% of Control) 41% 34% 56%72% — —

There was considerable variation among the mortars made from thedifferent cements in slump and strength. The Illinois Product wasnotable for its higher compressive strength at all time points tested.Without being bound by theory, this may be due to its greater surfacearea (see TABLE 18), which allows it to absorb carbon dioxide withrelatively less proportional impact on strength development. Strengthvs. surface area of carbonated mortar mixes with various surface areasis shown in FIG. 52.

Example 22

In this example, various admixtures were added to cement paste mixesexposed to carbon dioxide and their effects on slump after mixing weredetermined. The paste mix was 500 g cement, 250 g water. Holcim GUcement. 1% bwc CO2 was dosed, with mixing for one minute. The resultsare shown in TABLE 20.

TABLE 20 Effects of admixtures on slump of carbonated mortar ConditionPaste Spread (cm) (all doses expressed as 1 Min after Paste Spread (cm)% by weight of cement) mixing 10 Min after mixing Control 11.5 13.75 1%CO₂ 8.75 5 1% CO₂ + 1% Na₂SO₄ 9.75 4.25 1% CO₂ + 3% Na₂SO₄ 7.25 4 1%CO₂ + 5% Na₂SO₄ 4.75 4 1% CO₂ + 0.04% Citric Acid 6.75 4 1% CO₂ + 0.10%Gluconate 6.5 4.25 1% CO₂ + 0.15% Gluconate 9.25 9.75 1% CO₂ + 0.20%Gluconate 9.25 10.25 1% CO₂ + 0.05% Gluconate - 9.75 4.75 AfterCarbonation 1% CO₂ + 0.10% Gluconate - 10.75 11.775 After Carbonation 1%CO₂ + 0.15% Gluconate - 13.5 14 After Carbonation

Example 23

In this Example, sensors for carbon dioxide and moisture were used in amixing operation.

A precast operation was performed using the following mix components:

Aggregate Fine Shaw Resources 602 kg Sand Aggregate Coarse ⅜″ Coldstream200 kg Aggregate Coarse Granodiorite 839 kg Cement Cement Maxcem 286 kgAdmix Rheopel Plus 400 ml Admis Rheofit 900 350

Two carbon dioxide sensors were used, Sensor 1 positioned adjacent to anaccess hatch to the mixer and Sensor 2 positioned at the ejectionlocation of the mixer, at a door that discharges onto a belt. CO₂ dosewas increased or decreased depending on the overspill, as detected bythe two sensors.

They are involved in a two stage injection approach.

1. Fill—high flowrate to fill the mixer with CO₂

2. Supply—lower flowrate to maintain a supply as CO₂ is absorbed by theconcrete.

The PLC was programmed as follows to make changes based on the readingsof the CO₂ sensors:

Sensor 1 to be placed by door, sensor 2 placed by mixer exit (measureeach sensor separately)

If sensor 1 exceeds X ppm during flow 1, go to flow 2

If sensor 1 exceeds X ppm during flow 2, reduce flow by reducepercentage

If sensor 2 exceeds Y ppm ever, reduce max mix time by reduce time

If either sensor exceeds 5000 ppm for more than 5 mins, pop-up alarm onscreen

If either sensor exceeds 5000 ppm for more than 10 mins, shut off system

If either sensor exceeds 9000 ppm, shut system off

X and Y were programmable under each recipe (this allows change if aplant has a high CO₂ baseline due to dust etc.). Flow 1 was programmableand was the flow that was used to fill the headspace quickly (usually˜1500 LPM). Flow 2 was calculated by the PLC and was based on max mixtime, CO₂ dose and the total already in the headspace. Max mix time wasprogrammable and was the total desired injection time. Reduce percentageand reduce time were programmable and were determine by what percentageto reduce either the flowrate (thus reducing total CO2 dosage) or themax mix time (thus increasing flowrate to inject in shorter time).

The system was used over several batches and the results are shown inFIG. 53. The top line of FIG. 53 indicates the actual CO₂ dosed, and thesecond line indicates CO₂ detected in the mix. The efficiency of uptakevaried from 60 to 95%. The bottom two lines indicate maximum valuesdetected at Sensor 1 (all batches including Batch 3) and Sensor 2(Batches 4-10). Average values may produce a better result.

This example demonstrates that carbon dioxide sensors may be used toadjust the flow of carbon dioxide in a cement mixing operation,producing uptake efficiencies up to 95%.

Example 24

This example demonstrates the use of solid carbon dioxide (dry ice) as adelivery mode for carbon dioxide in mixing concrete.

A solid particle of carbon dioxide will sublimate when in contact withthe mix water, thereby releasing carbon dioxide gas over the period oftime required to consume the particle. To achieve an extended dosing ofcarbon dioxide, e.g., in a readymix truck, solid carbon dioxide can beadded in the desired mass and quantity, and in appropriate shape andsize, to effectively provide a given dose of carbon dioxide over adesired length of time. The shape and size of the solid carbon dioxidewill determine the total surface area of the solid; the greater thesurface area, the greater the rate of sublimation of the dry ice.

Two dosing procedures were used. In the first, dry ice in the form ofone inch pellets was used. In the second, a square slab with a 2″ by 2″cross section was cut to the appropriate length to provide the desireddose. Mixing was performed in either a small drum mixer (17 liters) orlarge drum mixer (64 liters), and the mixing was conducted with a coverunless otherwise indicated.

Pellet Delivery:

A mix design of 400 kg/m³ cement, 175 kg/m³ water, 1040 kg/m³ stone, and680 kg/m³ sand was used. Cement in one batch was 26.14 kg.

In a first batch, CO₂ at 0.5% bwc dose of pellets (34 g) was added withthe other mix materials and the concrete was mixed for 2 minutes. Uptakewas found to be 014% bwc, and a 1° C. temperature increase was noted.The dry ice pellets had not completely sublimed after 2 min of mixing.

In a second batch, CO₂ at 1.0% bwc dose of pellets (68 g) was added withthe other mix materials and the concrete was mixed for 4 minutes. CO₂uptake was 0.3% bwc with a 1° C. temperature increase. After 4 min ofmixing, all the dry ice pellets had completely sublimed.

In a third batch, CO₂ at 2.75% bwc dose of pellets (186 g) was addedwith the other mix materials and the concrete was mixed for 4 minutes.CO₂ uptake was 0.6% bwc with a 2° C. temperature rise; all dry icepellets were sublimed after 4 min of mixing.

With the use of pellets, uptake increased with increasing pellet dose,and pellets of this size and in these doses took 2 to 4 min tocompletely sublime. CO₂ uptake was low efficiency, and the gas uptakewas associated with mix stiffening.

Slab Delivery:

In a first test, the same mix design as for the pellet tests was used.The 2×2″ slab was cut to 5.5″ long for a dose of 2% CO₂ bwc. In a firstbatch, water was added in two additions. A first addition of water tow/c of 0.2 was performed, the dry ice slab was added and mixed for 40seconds. Final water was added to the total water amount and theconcrete was mixed for an additional 6 min. The CO₂ uptake was 0.95% andno temperature increase was observed. In a second batch, 4 serialaddition of slabs of dry ice were performed. All water was added to themix (w/c 0.44) then a dry ice slab was added for a dose of 2% bwc. Theconcrete was mixed for 6 min. CO₂ uptake was 0.67% and no temperatureincrease was observed. An additional slab of dry ice was added to themix, at 2% bwc for a total dose of 4% bwc, and a further 6 minutes ofmixing was performed. CO₂ uptake was 1.67%, and no temperature increasewas observed. An additional slab of dry ice was added to the mix, at 2%bwc for a total dose of 6% bwc, and a further 6 minutes of mixing wasperformed. CO₂ uptake was 2.33%, and a 3.5° C. temperature increase wasobserved. An additional slab of dry ice was added to the mix, at 6% bwcfor a total dose of 12% bwc, and a further 6 minutes of mixing wasperformed. CO₂ uptake was 3.44%, and a 5° C. temperature increase wasobserved. In this test, in which mixing was at full speed, all thecarbon dioxide was completely sublimed at the end of each mixing time.Subsequent tests were performed at lower speed representative of a truckin transit rather than a truck in initial mixing stage.

In a second test, the same mix design as for the pellets was used exceptthe final proportion of water was 200 kg/m³. Slow mixing (˜1 RPM) in a65 L mixer was performed, with a dry ice slab added 2 min after theinitial cement and water contact, for a dose of 2% bwc. Mixing wascontinued for a total of 36 min. CO₂ uptake was 0.95%, and a 3.5° C.temperature increase was observed. The slump of the concrete mix priorto CO₂ addition was 6″, and 3″ after 36 min of mixing under CO₂.

In a third test, the same mix design as for the pellet tests was used.Water was added to an initial w/c of 0.2, a dry ice slab was added for adose of 0.2% bwc, and the concrete mix was mixed for 40 s at full speed(45 rpm), then the remainder of the water was added, to a w/c of 0.45and the mix was mixed for 36 min of slow (transit, ˜1 RPM) mixing of thebatch in a 65 L mixer. CO₂ uptake was 0.75%, and a 1.5° C. temperatureincrease was observed. Slump was 5.5″ after 36 min of mixing. A controlslump (without carbon dioxide) was assumed to be ˜6″. Then another 2%bwc of dry ice slab was added, and the concrete was mixed at high speedfor an additional 11 min. CO₂ uptake was 1.66%. Slump decreased from5.5″ to 2.5.″

In a fourth test, the same mix design as for the pellet tests was used,except water was 195 kg/m³. Two batches were run in which dry ice at adose of 2% bwc was added 2 minutes after the initial cement and watercontact. In the first batch, the concrete was mixed with cover on at afast transit mix (˜2 RPM) for 30 min. CO₂ uptake was 1.3% bwc, and a 5°C. temperature increase was observed. Slump was 0″ after mixing,compared to 6.5″ slump in control (no carbon dioxide). In the secondbatch, mixing was done with cover off at a fast transit mix for 29 min.CO₂ uptake was 0.7% bwc, and a 0.2° C. temperature increase wasobserved. Slump was 3″ after 29 min mixing, compared to 6.5″ slump incontrol (no carbon dioxide).

This example demonstrates that the size and shape of dry ice can be usedto control delivery, and that various times of addition, mix rates,water contents, and other variables may be manipulated to modulate theamount of carbon dioxide taken up by the concrete and the effect of thecarbon dioxide on such factors as slump.

Example 25

This example illustrates the use of low-dose carbon dioxide to provideaccelerated hydration, early strength development and set, with minimalimpact on rheology and later-age strength.

Mortar Tests

In a first set of tests, mortars were prepared. Mortars were preparedwith 1350 g sand, 535 g cement, and 267.5 g water, and homogenized in apaddle-style mixer by mixing on low speed for ˜2 min, then samples wereremoved for CO₂ analysis and calorimetry. The mortar was then exposed toCO₂ gas at a flow rate of ˜0.15 LPM for 2 minutes and additional sampleswere removed. This same mortar was exposed to 3-7 successive rounds ofcarbonation total, with samples removed between each round.

In one test, Holcim GU cement was used. The levels of carbonation of themortar achieved in succeeding rounds of carbon dioxide exposure were 0,0.05, 0.10, 0.20, 0.48, and 0.70% bwc. FIG. 54 presents data onisothermal calorimetry power curves for the different levels ofcarbonation, showing that by carbonating the mortar the rate of cementhydration could be accelerated (curves shift to the left and becomesteeper with carbonation). The total heat evolution was also improved atearly ages with carbonation of the mortars (FIG. 55).

In addition, the onset of both initial and final set was accelerated bycarbonation, as indicated by penetrometer measurements and shown in FIG.56. For these measurements, mortar was prepared as follows: 5× batchsize in Hobart (normal batch scaled up 500% to use in a larger mixer)1337.5 g water, 2675 g cement 5175 g sand. Combined in Hobart mixer andhomogenized. Carbonated at 1.0 LPM for 5 rounds of 2 minutes (i.e. 0, 2,4, 6, 8, 10 minutes samples). Penetrometer measurement performed on lastsample (10 minutes total CO₂ exposure). Expected dose for 1 LPM for 10min is about 20 g of CO₂, for a total dose is about 0.74% bwc. FromEltra: carbon dioxide uptake estimated at 0.10% bwc. The low uptake mayhave been due to head space/flow rate. A Control was then cast forcomparison afterwards. 2× batch size in Kitchen Aid (smaller mixer):1070 g cement, 535 g water, 2070 g sand.

Similar results were seen for mortars prepared with Lafarge BrookfieldGU cement dosed at 0, 0.07 0.14, and 0.22% bwc carbon dioxide, as shownfor hydration in FIG. 57, as well as early strength development as shownin FIG. 58.

Concrete Tests

Tests were extended to concretes. In a typical experiment a batch ofconcrete was prepared with the following proportions: 16.0 kg sand,23.80 kg stone, 9.18 kg cement, 3.15 kg water. The concrete washomogenized in a drum-style mixer by mixing on low speed for ˜2 min andsamples were removed for CO₂ analysis and calorimetry. The concrete wasthen exposed to CO₂ gas at a flow rate of ˜2.0 LPM for 2 minutes andadditional samples were removed. This same concrete was exposed to threesuccessive rounds of carbonation in total, with samples removed betweeneach round. Total CO₂ uptake for succeeding rounds was 0, 0.10, 0.15,and 0.20% bwc.

In a first series, LaFarge Brookfield GU cement was used in theconcrete. Calorimetry power curves show acceleration of concrete. SeeFIG. 59. Calorimetry energy curves show an increased amount of heatreleased at all ages in the carbonated concrete. See FIG. 60. Earlystrength development was also accelerated in the carbonated concretes.See FIG. 61. In addition, set time measurements confirmed that theobserved acceleration of hydration translated into accelerated initial(500 psi) and final (4000 psi) set in the carbonated concrete. FIG. 62shows penetrometer readings over time for carbonated concrete(approximately 0.20% bwc CO₂ uptake) compared to uncarbonated.

Similar results were obtained in a second series, where concrete wasproduced with St. Mary's B cement; for example, carbonation at 0.08,0.17, and 0.35% bwc all produced increased 8-hour and 12-hourcompressive strength compared to uncarbonated control. See FIG. 63.

Other concretes were produced using St. Mary's HE cement and Holcim GUcement (carbonated at a single level of CO₂ uptake). The concretes werecarbonated at a constant carbon dioxide exposure of delivered carbondioxide at a rate of 0.10-0.15% bwc per minute over three minutes (2 minwith carbon dioxide flow and one minute of lid on mixing after delivery)for a total dose of 0.20-0.30% carbon dioxide bwc. Carbonation level was0.15% bwc in the Holcim GU mixture and 0.26% bwc in the St Mary's HEmixture. See Table 21.

TABLE 21 Properties of low dose carbonated concretes Initial Set FinalSet Strength Acceleration Acceleration Strength at 8 hr at 8 hr CementID (minutes) (minutes) (% of control) (MPa) St. Mary's HE 55 41 133 2.2Holcim GU 61 70 149 1.3

In an industrial trial, a truck carrying 2 m3 of concrete was deliveredto the lab, with a mix design of 1930 kg sand, 2240 kg stone, 630 kgLaFarge Brookfield GU cement, and 238 kg water. A sample of uncarbonatedconcrete was first removed from the truck to cast control samples. Thetruck was then subjected to 6 separate doses of 0.05% bwc CO₂. Enoughconcrete was removed to satisfy casting demands following each dose (˜60L). The fresh properties of the concrete are shown in Table 22.

TABLE 22 Fresh properties of readymix concrete at low dose carbonationTotal Temp at Air Defoamer Mighty CO₂ dose Time of discharge SlumpContent Dose 21ES dose Sample # Sample ID (bwc) discharge (° C.)(inches) (%) (% bwc) (% bwc) 1 Control 0 8:45 14.7 3.5 1.5 0.10 0.10 2CO₂-1 0.05 8:50 16.4 3.5 n/a 0.10 0.10 3 CO₂-2 0.10 9:04 16.7 3.5 n/a0.10 0.10 4 CO₂-3 0.15 9:12 18.0 3.0 n/a 0.10 0.10 5 CO₂-4 0.20 9:2618.4 3.0 n/a 0.10 0.10 6 CO₂-5 0.25 9:35 18.5 1.5 n/a 0.10 0.10 7 CO₂-60.30 9:50 18.7 2.0 n/a 0.10 0.15

In general, the compressive strength of the concrete specimens increasedwith each additional round of carbonation. This was most evident atearly ages (up to 74% increase at 12 hours) but persisted until laterages (5% compressive strength increase at 7 days). See FIGS. 64 (12hours), 65 (16 hours), 66 (24 hours), and 67 (7 days).

This example illustrates that the use of low-dose carbon dioxide inmortar and concrete mixes can accelerate set and strength developmentcompared to uncarbonated mortar and concrete mixes.

Example 26

This example demonstrates the use of sodium gluconate in a dry mixconcrete, either carbonated or uncarbonated.

The mix was 200 g stone, 1330 g sand, 330 g Holcim GU cement, and 130 gwater. The mixing cycle was:

Mix aggregates and water for 30 s

-   -   Add cement and mix 30 s    -   60 s mixing, with carbonation if called for    -   add admixtures and mix 30 s    -   Compact cylinders using Proctor hammer    -   Dosages employed were 0, 0.02%, 0.04% and 0.06% sodium gluconate        by mass of cement.

FIG. 68 shows the CO₂ uptake of carbonated specimens. The masses of thecylinders prepared, a proxy for density since all cylinder volumes aresubstantially the same, showed that carbonation resulted in an 8.4% massdeficit in comparison to the control, but that the addition of sodiumgluconate increased the mass of the carbonated specimens, proportionalto the dose, so that at a dose of 0.06% sodium gluconate, the massdeficit was reduced to 5.5%, whereas none of the three sodium gluconatedoses had an effect on the compaction of the control samples. See FIGS.69 and 70. Retardation was quantified through calorimetry by determiningthe amount of energy released through the first 6 hours following themix start. Carbonation caused a decrease in energy released, as did theaddition of sodium gluconate; in carbonated specimens the reduction inenergy released was 19% at the highest sodium gluconate dose, whereas inuncarbonated specimens the reduction in energy released was 53% at thehighest sodium gluconate dose. See FIGS. 71 and 72.

Example 27

This example demonstrates the effects of increasing free lime on carbondioxide uptake and hydration.

In a first test, mortars were prepared with added CaO (1.5% bwc), NaOH(2.2% bwc), or CaCl₂ (3% bwc), carbonated, and compared to control. Astandard mortar mix of 535 g cement, 2350 g sand, and 267.5 g water wasused. The sand and water were combined and mixed for 30 s, followed bycement addition (with added powder if used) and an additional 60 smixing. Initial temperature was recorded, then the mortar was mixed for60 s under 20 LPM CO₂ flow, mixing was stopped and temperature recordedand sample removed for CO₂ analysis, then mixing and CO₂ exposure wasresumed for another 60 s and sampling occurred, for a total of 5 min ofCO₂ exposure. The results are shown in FIG. 73. Addition of the alkalispecies, free lime (CaO) or NaOH, increased the rate of CO₂ uptake,while the addition of CaCl₂ decreased the uptake rate. The rates ofuptake were: 0.34% CO₂ uptake/min (no additive); 0.56% CO₂ uptake/min(CaO), a 66% increase; 0.69% CO₂ uptake/min (NaOH), a 104% increase; and0.23% CO₂ uptake/min (CaCl2), a 34% decrease.

In a second test, two test mortars were compared, one conventionalmortar and one that included an addition of 1.5% CaO bwc. The mortarmixes were as in the first test. The cement used had a free lime contentof 0.31% bwc before addition of extra CaO; this is considered to be alow free lime level. The mixing mortar was subjected to 0, 30, 60, or 90s of CO₂ at 20 LPM, and hydration was measured by calorimetry. Energyrelease was followed up to 24 hours at 6 hour intervals.

The results are presented in FIG. 74. When control (no CaO addition)carbonated vs. uncarbonated mortars were compared, energy release with30 s CO₂ was 19% greater in the carbonated compared to uncarbonated at 6hours, declining to 7% lower at 24 hours; energy release with 60 s CO₂was 23% greater in the carbonated compared to uncarbonated at 6 hours,declining to 12% lower at 24 hours; energy release with 90 s CO₂ was 21%greater in the carbonated compared to uncarbonated at 6 hours, decliningto 17% lower at 24 hours. See FIG. 75. In general, addition of CaO tothe mix both increased CO₂ uptake for a given time of exposure, andincreased the energy release at a given time point, compared to sampleswithout CaO addition. When compared to a control mortar that containedno added CaO, mortars with added CaO showed energy release at 97-99% ofcontrol at all time points in uncarbonated samples; in samples exposedto 30 s CO₂, mortars with added CaO showed energy release 20% higherthan mortars with no added CaO at 6 hours, decreasing to 11% higher at24 hours, and CO₂ uptake was 56% greater than in mortars with no addedCaO; in samples exposed to 60 s CO₂, mortars with added CaO showedenergy release 33% higher than mortars with no added CaO at 6 hours,decreasing to 15% higher at 24 hours, and uptake was 151% greater thanin mortars with no added CaO; in samples exposed to 90 s CO₂, mortarswith added CaO showed energy release 23% higher than mortars with noadded CaO at 6 hours, decreasing to 9% higher at 24 hours, and uptakewas 151% greater than in mortars with no added CaO. See FIG. 76.

This example demonstrates that free lime (CaO) addition to a mortar bothimproves the rate of carbon dioxide uptake as well as hydration, whencompared to mortar without added free lime

Examples 28-32 are directed to delivery of low doses of carbon dioxideto ready mix trucks, as a gas (Example 27) or liquid that converts tosolid and gas (Examples 29-32), under various conditions.

Example 28

This example is an illustration of low dose of gaseous carbon dioxidetreatment of a concrete mix in the drum of a ready mix truck at a timesignificantly after the batching of the concrete, and its effects onearly strength.

The carbon dioxide was dosed into the drum of a ready mix truck. Carbondioxide was gaseous. The carbon dioxide was added to the mix beginningapproximately 70 min after batching, in multiple stages to give aconcrete mix with increasingly greater doses of carbon dioxide so thatthe final addition was approximately 135 min post batching. Thus thedosing of CO₂ was well after mixing started, akin to supplying CO₂ to atruck in transit or at a job site rather than during batching.

Mix design was 30 MPa slab mix, 2 m³ load, truck less than half full

-   -   Sand 1930 kg    -   Stone 2240 kg    -   GU Cement 630 kg    -   Water 238 kg

Admixes were added at the test site prior to any sampling—defoamer 0.10%bwc, superplasticizer (Mighty ES) 0.10% bwc. Mighty ES was increased forfinal sample.

CO₂ was added to the drum from a gas tank with a regulator. Flow was ˜80LPM for 2 minutes for each CO₂ dose. Line Pressure was 70 psi. Truckfaster mix (25 RPM) “post dose” for ˜60 s. Transit mix (slow, 5 RPM)remaining time.

Dosing was in a serial fashion on the same batch of concrete—dose,sample, next dose, sample, next dose, etc.

Time of discharge indicates when concrete was sampled. Dosing would haveoccurred within the five minutes immediately preceding.

Table 23 shows the conditions for each sample:

TABLE 23 Conditions for various samples of low dose carbon dioxideSample ID Control CO2-1 CO2-2 CO2-3 CO2-4 CO2-5 CO2-6 Time of Discharge74 79 93 101 115 124 139 (min) Total CO₂ Dose 0 0.05% 0.10% 0.15% 0.20%0.25% 0.30% (% bwc) Temperature (° C.) 14.7 16.4 16.7 18 18.4 18.5 18.7Slump (inches) 3.5 3.5 3.5 3 3 1.5 2 Air Content (%) 1.5 n/a n/a n/a n/an/a n/a Defoamer 0.10% 0.10% 0.10% 0.10% 0.10% 0.10% 0.10% (% bwc)Mighty ES 0.10% 0.10% 0.10% 0.10% 0.10% 0.10% 0.15% (% bwc) CO₂ Uptake —inconclusive (% bwc)

12-hour, 16-hour, 24-hour, 7-day, 28-day strengths are shown in Tables24 (absolute values) and 25 (values relative to control, uncarbonatedconcrete). Three specimens were taken at each age as 4″×8″ cylinderswith reusable end caps. Specimens were kept in moist curing storageuntil testing. Calorimetry data is shown in FIGS. 77A (power vs. time)and 77B (energy vs. time) for Control, CO2-1, 2, and 3 and in FIGS. 78A(power vs. time) and 78B (energy vs. time) for Control, CO2-4, 5, and 6.

TABLE 24 Compressive strengths, absolute (MPa) ID Control CO2-1 CO2-2CO2-3 CO2-4 CO2-5 CO2-6 12 hr 1.7 2.0 2.0 2.7 2.7 2.4 2.9 16 hr 5.9 6.46.0 6.5 6.8 6.0 6.5 24 hr 12.8 13.3 13.3 13.5 13.7 13.5 13.9  7 d 31.531.7 31.3 33.1 32.9 32.6 33.1 28 d  37.3 37.9 38.7 38.0 38.9 38.7 39.1

TABLE 25 Compressive strengths, relative to uncarbonated ID ControlCO2-1 CO2-2 CO2-3 CO2-4 CO2-5 CO2-6 12 hr 100% 123% 119% 166% 163% 145%174% 16 hr 100% 109% 103% 111% 116% 102% 110% 24 hr 100% 104% 104% 105%107% 105% 109%  7 d 100% 101% 100% 105% 105% 104% 105% 28 d  100% 101%104% 102% 104% 104% 105%

The set also slightly accelerated in highest CO₂ dose.

The results show that in all cases, even at the lowest dose of CO2(0.05% CO2 delivered, bwc), there was an increase in early strength. Ingeneral, the strength benefit of CO₂ broadly corresponded to increasingdose. The benefit was most pronounced at the earliest ages, thoughtthere was still a small benefit at 7 and 28 days.

This example demonstrates that very low doses of carbon dioxide, addedto concrete mixes after batching, cause marked increases in earlystrength development. This was true even for the lowest dose of carbondioxide, 0.05%; at such low doses carbonation of the concrete may not bedetectable, but nonetheless the carbon dioxide is acting in a mannersimilar to an admixture, in this case as a potent accelerant of earlystrength development.

Example 29

This example is an illustration of low dose of gaseous and solid carbondioxide treatment of concrete in the drum of a ready mix truck, from aliquid source of carbon dioxide, at a time significantly after thebatching of the concrete, and its effects on early strength.

The 30 MPa slab mix design of Example 28 was used. 2 cubic meters ofconcrete were produced, truck was less than half full. Admixes added attest site TK—ADVA 140 superplasticizer 0.20% bwc, sodium gluconate 0.05%bwc.

The CO₂ supplied as a liquid, from a dewar with a hose attached with afitting on the end and an orifice of defined size, 5/64 inch. The dosingwas calculated based on a series of assumptions and is approximate. Theassumptions were: 1) that the carbon dioxide was 100% liquid in the lineupstream of the orifice, i.e., no phase 2 flow; 2) the flow was based onan equation (not directly measured); and 3) that there was no pressuredrop in the line, that it was a constant 300 psi. The tube was directedinto the drum of the ready mix truck so as to deliver the gaseous andsolid carbon dioxide to the surface of the mixing concrete.

Table 26 shows the conditions for each sample. Staged dosing wasperformed, with the first dose was delivered approximately 45 min afterbatching, and the final dose approximately 110 min after batching. Thus,as with Example 28, dosing with CO₂ was well after mixing started, akinto supplying CO₂ to a truck in transit or at a job site rather thanduring batching.

TABLE 26 Conditions for each sample Sample ID Control CO2-1 CO2-2 CO2-3CO2-4 CO2-5 CO2-6 Time of Discharge 28 48 63 78 88 99 113 (min) TotalCO₂ Dose 0 0.10% 0.20% 0.30% 0.40% 0.50% 0.60% (% bwc) Temperature (°C.) 19.5 20.7 20.8 21.2 21.5 22.3 23.2 Slump (inches) 7 4.5 3.75 4 32.75 2 Air Content (%) 1.8 — — — — — 1.8 CO₂ Uptake (% bwc) 0.00 −0.090.01 −0.01 0.01 0.07 0.10

8-hr, 12-hour, 24-hour, 7-day, and 28-day strengths are shown in Tables27 (expressed as absolute strengths) and 28 (expressed as relative touncarbonated control). Three specimens were taken at each age as 4×8″cylinders with reusable end caps. Specimens were kept in moist curingstorage until testing. Calorimetry data is shown in FIGS. 79A (power vs.time) and 79B (energy vs. time) for control, CO2-1, 2, and 3 and in FIG.80A (power vs. time) and 80B (energy vs. time) for control, CO2-5 and 6.

TABLE 27 Compressive strengths, absolute (MPa) Control CO2-1 CO2-2 CO2-3CO2-4 CO2-5 CO2-6 8 hr 1.8 1.9 1.7 1.8 1.8 1.8 1.9 12 hr 6.1 6.4 6.1 6.46.3 6.8 7.0 24 hr 13.9 14.1 14.9 14.9 15.2 15.6 15.4 7 day 24.8 25.727.0 26.1 28.0 27.7 28.7 28 day 34.5 34.0 34.0 33.8 35.6 35.8 35.8

TABLE 28 Compressive strengths, relative to uncarbonated Control CO2-1CO2-2 CO2-3 CO2-4 CO2-5 CO2-6 8 hr 100% 107%  91%  97% 100%  98% 104% 12hr 100% 104% 100% 105% 103% 112% 114% 24 hr 100% 101% 107% 108% 110%113% 111% 7 day 100% 104% 109% 105% 113% 112% 116% 28 day 100%  99%  99% 98% 103% 104% 104%

calorimetry shows that the carbonation treatment has increased the heatrelease associated with the hydration of aluminates, see FIGS. 79A, Band 80A, B, and Tables 27 and 28, supporting the use of calorimetry asan alternative or additional marker to strength measurements indetermining desired or optimal dosing conditions for carbonation of aconcrete mix.

Strength benefit of CO₂ broadly corresponded to increasing dose. Set wasslightly accelerated in highest CO₂ dose.

This example demonstrates that dosing carbon dioxide into a ready mixdrum by using a liquid to solid/gas conversion as the carbon dioxide isdosed is viable.

Example 30

This example is an illustration of low dose of gaseous and solid carbondioxide treatment of concrete in the drum of a ready mix truck, from aliquid source of carbon dioxide, at a time significantly after thebatching of the concrete, and its effects on early strength. Theconcrete mix included an SCM (slag). Two trials were conducted onconsecutive days. On the first day the carbon dioxide was dosed atvarious times up to about 70 minutes after batching. On the second daythe carbon dioxide was dosed much earlier after batching, at about 20minutes.

One truck of 4 m³ of concrete was batched filled with a 25 MPa floor mixdesign, below:

Component Mass (kg/m³) Sand 959 Stone 1080 Cement 212 Slag 53 Water 155SuperP (mL) 190

On the first day of the trial, one truck received three serial doses ofCO₂ after the control sample. On the second day of the trial, there wasonly one dose of CO₂. The injection of CO₂ proceeded for 30-90 secondswith an additional 90-180 seconds of high speed mixing after theinjection was completed. The requested load of concrete was firstbatched into the truck before transport to the wash rack where the batchreceived final water adjustments by the truck operator. Upon completionof the batch adjustments a sample of uncarbonated (control) concrete wasremoved, a slump test was performed, and test specimens were cast. Thetruck was then subjected to three sequential doses of carbon dioxidewith assessment of slump and casting of the treated concrete betweeneach round. The time between the start of mixing and the carbon dioxideapplication was recorded. All of the test samples came from the sametruck to maximize the experimental results from a single batch and tominimize any batch-to-batch variation that may have arisen. Thesequential dosing of carbon dioxide was pursued to determine an optimumdose.

Whereas the trial of example 29 involved a tube held in position, thetrials from hereafter used a rigid injector tube. A clamp allowed it tobe fixed to the truck structure and held in place. This type of systemis similar to a portable system for dosing carbon dioxide that could bemounted on the truck itself, so that dosing can be done at any timebefore, during or after batching, as a single dose or as staged doses.

Conditions are summarized in Table 29

TABLE 29 Conditions in trial Estimated Discharge Total CO₂ Truck SampleTime CO₂ Dose Uptake Slump Temp (day) Code Condition (min) (% bwc) (%bwc) (inches) (° C.) 1 1401 Control 23 — — 3.5 23.9 1402 CO₂ 45 0.10%inconclusive 3.0 — 1403 CO₂ 59 0.30% inconclusive 3.0 25.6 1404 CO₂ 740.60% inconclusive 2.0 26.5 2 1501 Control 10 — — 2.5 23.7 1502 CO₂ 200.30% inconclusive 2.0 24.9

Trials were run on two consecutive days. Compressive strengths at 1, 3,7, 28, and 56 for samples taken on the first day are shown in FIGS.81-85 and calorimetry for first-day samples is shown in FIG. 86A (powervs. time) and 86B (energy vs. time). Three specimens were used for 1day, two specimens at all other ages. 4×8″ cylinders were subjected toend grinding to create planar faces and kept in moist curing storageprior to testing. For the second day, FIGS. 87-91 show strength at 1, 3,7, 28, and 56 days and FIG. 92A (power vs. time) and 92B (energy vs.time) show calorimetry. It can be seen that for both days, shifts in thecalorimetry curves match the increases in strength, with the greatestshift seen for the dose of carbon dioxide on a given day that gave thegreatest acceleration of strength development, see, e.g., FIG. 86A.Three specimens were used for 1 day, two specimens at all other ages.4×8″ cylinders were subjected to end grinding to create planar faces andkept in moist curing storage prior to testing.

The carbon dioxide injection did not appear to have any effect on theinduction period. The acceleratory stage of hydration for each samplewas underway by 4 hours. By 7 hours the heat evolution of the carbonatedsamples occurred at an increased rate (as noted in a shift to the leftof the shape of the curves) where the effect was greater with thegreater dose of carbon dioxide. Further, the heat release at the peak ofthe early hydration was found to increase in magnitude and be shifted toearlier times as the carbon dioxide dose increased. An alternateinterpretation of the data considers the total energy released withtime. The energy release relative to the control can be quantified atvarious ages and used as a metric of hydration progress. It is shownthat at 6 hours the carbonated batches had released about 10% lessenergy than the control. The low dose had matched the control by 11hours and remained equivalent thereafter. The second dose of CO₂ reached101% of the control at 9 hours before improving to 12% better at 12hours and finishing at 6% more energy released through 20 hours. Thehighest dose reached 102% of the control at 10 hours, 13% greater at 12hours and 4% increase through 20 hours. It is observed that the carbondioxide may have slightly slowed the hydration in the first 8 hours butin the 10 to 14 hour range an accelerating effect could be realized inthe two higher doses. This potentially corresponds to a performancebenefit such as a higher strength at these times.

Resistance testing was also performed, following AASHTO TP 95-11“Surface Resistivity Indication of Concrete's Ability to Resist ChlorideIon Penetration” Electrical resistivity and assessed risk of chloridepenetration were measured.

Standards are summarized in Table 30, below.

TABLE 30 ASTM and AASTO standards AASHTO TP95-11 ASTM C1202 28 dayElectrical 56 day RCPT Resistivity Chloride Penetration Coulombs ΩmHigh >4000   <45.93 Moderate 2000-4000 45.93-91.86 Low 1000-200091.86-183.7 Very Low  100-1000 183.7 to 1837 Negligible  <100 >1837

Results are summarized in Table 31.

TABLE 31 Resistivity results for carbonated concretes Average BulkElectrical Resistivity (Ωm) and Chloride Penetration Risk for five testages (days) Sample 1 3 7 28 56 1401 8.9 19.3 33.6 78.7 106.5 1402 8.818.9 25.5 74.1 112.0 1403 8.7 18.8 24.7 67.1 97.7 1404 8.9 20.3 24.170.2 101.8 1401 High High High Moderate Low 1402 High High High ModerateLow 1403 High High High Moderate Low 1404 High High High Moderate Low1501 9.1 16.2 22.9 54.7 85.0 1502 8.9 16.1 22.0 50.8 82.8 1501 High HighHigh Moderate Moderate 1502 High High High Moderate Moderate

The CO₂ treatment did not impact the resistivity with values for thecontrol & CO₂ “moderate” at 28 days and “low” at 56 days.

The use of staggered vs. single batch indicates that the staggered batch(1403), when compared to the single dose (1502), both at 0.30%, produceda more robust increase in strength. This may be due to the batching, orit may be due to the time the carbon dioxide was applied after mixing(60 min vs 20 min), or both. The highest benefit was in the batch withthe three-stage dose (1404), with benefit from 13 to 26% across the testperiod. Calorimetry results showed acceleration and greater energyrelease for the staggered samples.

This example demonstrates that carbon dioxide at low doses increasesearly strength with benefits maintained at later time points, that thecarbon dioxide did not affect resistivity, and that the time afterbatching of carbon dioxide addition and/or staging may affect themagnitude of the increase in early strength. Finally, the Exampleillustrates the use of carbon dioxide in a mix containing an SCM (slag),with beneficial results seen for the carbonated vs. uncarbonatedconcrete.

Example 31

This example is a repeat of Example 30, with some modifications. Thesame mix design was used (i.e., concrete with SCM). One truck of 4 m³ ofconcrete received three serial doses of CO₂ after the control sample.The injection of CO₂ proceeded for 30-90 seconds with an additional90-180 seconds of high speed mixing after the injection was completed.The same carbon dioxide injection system as Example 30 was used. Thetrial of Example 31 was a repeat of Example 30 to increase confidence inthe results. However, while delivering a CO₂ injection to a truckstopped at the wash rack (as in Example 30) is potentially feasible,breaking the delivery into multiple doses represents a possible delaythat is preferably avoided and is not universally applicable. Manyexamples exists wherein concrete is batched and mix centrally therebyprecluding the need for a wash rack and a related pause. Thus Example 31included an alternate CO₂ injection mode (sample code 805, below)wherein the gas was added during the initial batching/mixing phase.

The second truck had one dose of CO₂, equivalent to two doses of thefirst truck (0.30% carbon dioxide bwc) but was dosed during mixing.Conditions for the samples in the trial are given in Table 32.

TABLE 32 Conditions for samples Est Discharge Total CO₂ Sample Time CO₂Dose Uptake Slump Temp Truck Code Condition (min) (% bwc) (% bwc)(inches) (° C.) 1 801 Control 21 — — 3.5 22.4 802 CO₂ 30 0.10%inconclusive 3.0 24.0 803 CO₂ 46 0.30% inconclusive 2.5 24.7 804 CO₂ 550.60% inconclusive 1.5 27.3 2 805 CO2 —  0.3% — 3.0 23.3

Absolute compressive strengths are shown in Table 33 and compressivestrengths relative to uncarbonated control are shown in Table 34. FIGS.93A (power vs. time) and 93B (energy vs. time) show calorimetry data forthe various carbon dioxide doses.

TABLE 33 Compressive strengths, absolute Compressive Strength (MPa)Control CO2 CO2 CO2 CO2 0801 0802 0803 0804 0805  1 day 8.0 8.0 8.6 8.79.2  3 day 14.8 15.8 16.6 16.1 18.6  7 day 19.2 20.4 21.4 22.1 23.2 28day 30.8 32.0 33.9 32.8 35.5 56 day 32.8 27.9 37.9 36.4 38.7 91 day 36.938.4 39.1 39.5 42.5

TABLE 34 Compressive strengths, relative Strength Relative to theControl Control CO2 CO2 CO2 CO2 0801 0802 0803 0804 0805  1 day 100% 99%106% 108% 114%  3 day 100% 107% 112% 109% 126%  7 day 100% 106% 111%115% 121% 28 day 100% 104% 110% 107% 115% 56 day 100% 85% 116% 111% 118%91 day 100% 103% 106% 107% 115%

As in Example 30, when carbon dioxide was dosed in stages, an increasingearly (1 day) strength benefit was seen with increasing dose, though theeffect was not consistent at the later time points. However, unlikeExample 30, the single dose sample, 0805, was superior in strength atevery time point to the same dose, delivered in two stages (0803). Inthis Example, the single dose was given during batching rather thanafter batching. This method outperformed all of the staged doses atevery time point.

Calorimetry trends were consistent with Example 30, that is, dosesgiving the greatest acceleration of strength also showed the greatestshift in the calorimetry curves. The data considered as energy shows themagnitude of the effect from the carbon dioxide. The lowest dosereleased 20% more energy than the control through 2 hours. The benefitdeclined to 7% at 7 hours before increasing to 13% at 10 hours andthereafter the declining to be equivalent to the control. The middledose of CO₂ was 41% higher than the control at 2 hours with the benefitdeclining to 9% at 8 hours. The energy release jumped to 16% ahead ofthe control at 10 hours before declining to be equivalent to thecontrol. For the highest dose the energy was between 92% and 99% of thecontrol in the first 9 hours before spiking to be 9% ahead andthereafter declining to be equivalent to the control. It is evident thatthe lower doses of CO₂ had an effect on the very early hydration and alldoses had an effect notably around the 10 hour mark. The shape of thepower curves suggests that this time period is consistent with the endof the acceleration period when the initial silicate hydration starts toslow down.

The batch that was dosed with CO₂ during batching (805) showed acalorimetry response that appeared to show some retardation relative tothe control (data not shown). Heat evolution was slower across the 7 to13 hour interval. After lagging to 83% of the control through 11 hoursthe hydration accelerated and was 5% ahead at 15 hours thereafterincreasing to 7% at 20 hours.

Bulk resistivity measurements were taken according to the protocol usedin Example 31. The results are shown in Table 34A.

TABLE 34A Bulk Resistivity (Ω · m) and chloride penetrability risk fortest specimens at five different ages Sample Code Condition 1 day 3 day7 day 28 day 91 day 801 Control 9.6 14.9 21.0 58.3 123.4 802 0.1% CO₂9.6 16.4 21.6 56.8 122.2 803 0.3% CO₂ 9.2 15.9 20.9 59.6 123.7 804 0.6%CO₂ 9.2 16.1 20.7 50.3 112.9 805 0.3% CO₂ 10.1 18.0 23.3 61.8 129.8 801Control High High High Moderate Low 802 0.1% CO₂ High High High ModerateLow 803 0.3% CO₂ High High High Moderate Low 804 0.6% CO₂ High High HighModerate Low 805 0.3% CO₂ High High High Moderate Low

The bulk resistivity measurements were consistent with what was observedin Example 31 insofar as the assessments of the carbonated batches wereequivalent to the control. The chloride penetrability risk for allsamples was assessed to be moderate at 28 days and low at 91 days.

This example confirms the consistent benefit of low dose carbon dioxideon early strength development and demonstrates the effect of time ofcarbon dioxide addition on the magnitude of the strength benefit. Thecarbon dioxide addition during batching would be equivalent of dosingdone at the yard, whereas the other times of carbon dioxide additionduring the staged addition are akin to dosing during transit and/or atthe job site.

Example 32

In this example, carbon dioxide was added to concrete in ready mixtrucks almost immediately after batching, using the same dose in twodifferent trucks but different time for delivery of the carbon dioxide.A mix design was used containing an SCM, in this case, fly ash.

Three trucks were used, each 8.5 m³, thus these were full trucks;

The mix design was:

-   -   Sand 868 kg    -   Stone 1050 kg    -   Cement 282 kg    -   Fly ash 68 kg

CO₂ was supplied as a liquid using a wand directing it into the drum. Inthis Example the system would be equivalent to a permanent system at thebatching plant.

The CO₂ was supplied to the concrete immediately after the truck leftthe batch house. There was approximately 4 min of batching/mixing in thehouse, 2 min reorientation of the truck, and then the CO₂ was added, asa single dose per truck. This would be the equivalent of a dosing schemeat the batching plant. Only one dose was given per truck, which was thesame dose for each truck but given over two different time periods.Conditions for the trucks in the trial are given in Table 35.

TABLE 35 Conditions for samples in trial Total CO₂ Dose CO₂ Slump TempTruck Condition (% bwc) Uptake (% bwc) (inches) (° C.) 1 Control — — 5.521.1 2 CO₂-1 0.50% over 4 min inconclusive 2.0 20.7 3 CO₂-2 0.50% over 2min inconclusive 6.0 21.6

Compressive strengths were measured at 1, 4, 7, and 28 days. Absolutecompressive strengths are given in Table 36; compressive strengthsrelative to control are given in Table 37. Calorimetry data is shown inFIGS. 94A (power vs. time) and 94B (energy vs. time). Three specimenswere used at all ages as 4×8″ cylinders with reusable end caps. Moistcuring storage was used prior to testing.

TABLE 36 Compressive strengths, absolute Compressive Strength (MPa)Control CO2-1 CO2-2 1 day 15.2 18.9 14.2 4 day 31.4 33.4 28.3 7 day 31.737.6 33.1 28 day  44.9 47.8 42.0

TABLE 37 Compressive strengths, relative to control Strength Relative tocontrol Control CO2-1 CO2-2 1 day 100% 125% 93% 4 day 100% 107% 90% 7day 100% 119% 105%  28 day  100% 106% 94%

The strength at every time point was superior in the concrete from thetruck dosed over 4 min (CO2-1) compared to the truck dosed over 2 min(CO2-2), possibly because the slower delivery allowed the fresh concretemore time to react without swamping the system.

The example illustrates that another possibility for carbon dioxidedosing can be after water is added to the mix and mixing starts, butwithin minutes after mixing starts. In facilities with a wash rack,where the truck is rinsed prior to departure and the consistency of theconcrete is checked, a truck may pause for about ten minutes. Thisoffers an opportunity for carbon dioxide dosing in this time frame. ThisExample also illustrates the use of the low dose carbon dioxide with amix containing an SCM, and beneficial results in early strengthdevelopment compared to uncarbonated control. Finally, this examplefurther illustrates that changes in calorimetry data correlate withearly strength changes.

Example 33

In this example, a method for screening a particular cement to determineoptimal carbon dioxide dosing was performed.

The mix design was Sand 1350 g, Cement 535 g, Water 267.5 g

The procedure was:

-   -   Combine sand and water in kitchen aid mixer—mix 30 s on setting        #2    -   Add cement—mix 30 s on setting #2    -   Remove uncarbonated sample for calorimetry and CO₂ analysis    -   Carbonate for 2 minutes at 0.15 LPM    -   Remove sample #2 for calorimetry and CO₂ analysis    -   Repeat steps 4 and 5 as many times as desired

In this example, Lafarge Brookfield cement was used, but the proceduremay be used for any cement to screen for optimal carbon dioxide dosing.

An increase in heat released at early ages (acceleration) was observedfor all CO₂ doses. Lower uptakes are better at later ages; higher doseshad negative impact on total energy. See FIGS. 95-99. FIG. 95 showscalorimetry curves (power vs. time) for 5 mortars with varying levels ofCO₂ uptake (1 sample before carbonation followed by 5 rounds ofcarbonation, each for 2 min at 0.15 LPM). FIGS. 96-99 give the resultsof the analysis of energy released relative to the uncarbonated controlat 4, 8, 12, and 16 hours.

This example illustrates a method for rapidly determining optimal carbondioxide dose for a particular cement to be used in, e.g., a concretemix, by using calorimetry as an alternative or additional marker tostrength development.

Example 34

In this example, delivery of CO₂ via carbonated water was tested withthe carbonated water being used as the sole water source for a concrete.

If some or all of the mix water in a wet mix concrete is carbonated, itcan contain an amount of CO₂ that can be sufficient to obtain a desireddose of carbon dioxide in the concrete by the use of carbonated mixwater alone, depending on the desired dose; this is certainly true formany low dose mixes. For example, consider a mix that is 350 kg/m³ ofcement. A dose of CO₂ of 0.5% bwc would be 1.75 kg of CO₂. At w/c of0.45 there is 157.5 kg of water in a cubic meter. So a dose of CO₂ of0.5% would be 11.1 g CO₂/L water. This amount of carbon dioxide could becarried by carbonated water at about 94 psi and 25° C. Cooler watercould carry more, particularly if a fraction of the water is to remainuncarbonated. Lower doses than 0.5% are easily achievable usingcarbonation of the mix water, or a portion of the mix water.

Thus, we explored the use of carbonated water as a carrier of the lowdose of CO₂.

Mix Procedure A—Control

-   -   1. Combine 1350 g sand and 53.5 g water in bowl—mix 30 s    -   2. Add 535 g cement to bowl—mix 30 s    -   3. Add 214 g water to bowl over ˜10 s—mix 30 s    -   4. Mix mortar for additional 2 minutes

Mix Procedure B—CO₂

-   -   1. Combine 1350 g sand and 535 g cement in bowl—mix 30 s    -   2. Add 267.5 g carbonated water to bowl—mix 30 s. Carbonated        water was Perrier water.    -   3. Mix mortar for additional 2 minutes

In this trial, the mix water in the carbonated case was added as oneaddition, and all of the mix water was carbonated.

Surprisingly, calorimetry indicated retardation of about 2 to 4 hours.See FIGS. 100 (power vs. time) and 101 (energy vs. time). The time atwhich the carbonated mix water is introduced may be important, and thata “pre wet” step before the carbonated water addition can be used inorder to “prime” the reactions in the hydrating cement so that when thecarbonated water is then added the desired effect on strengthacceleration is seen.

Example 35

In this example the effects of low dose carbonation on reversing theretardation of early strength development in concretes containing anSCM, in this case, fly ash, was studied.

The procedure was as follows:

-   -   Combine 1350 g sand and 267.5 g water in bowl—mix 30 s    -   Add 428 g cement and 107 g fly ash (80/20 blend)—mix 60 s    -   Remove sample for calorimetry and bakeoff    -   Dose CO₂ at 0.15 LPM for 2 minutes    -   Remove sample for calorimetry and bakeoff    -   Dose CO₂ at 0.15 LPM for 2 minutes (4 minutes total CO₂ dose)    -   Remove sample for calorimetry and bakeoff    -   Dose CO₂ at 0.15 LPM for 2 minutes (6 minutes total CO2 dose)    -   Remove sample for calorimetry and bakeoff

Cements used in the trials were: Argos, Cemex, Holcim, Titan Roanoake.

Fly ashes used in the trials were: Venture Belews creek, SEFA Wateree.

The results are shown in FIGS. 102-109. In each Figure, the CO₂ uptakefor the particular mix is given for the three different carbon dioxidedoses, and calorimetry, reported as total energy released at a discretetime interval (8, 16, and 23 hours after mixing) is shown, as a percentof uncarbonated control. FIG. 102 shows results for an Argoscement+Venture FA mix. FIG. 103 shows results for a Cemex cement+VentureFA mix. FIG. 104 shows results for a Holcim cement+Venture FA mix. FIG.105 shows results for a Titan Roanoake cement+Venture FA mix. FIG. 106shows results for an Argos cement+SEFA FA mix. FIG. 107 shows resultsfor a Cemex cement+SEFA FA mix. FIG. 108 shows results for a Holcimcement+SEFA FA mix. FIG. 109 shows results for a Titan Roanoakecement+SEFA FA mix. In summary, for Venture ash: In all four cements anincreased heat of hydration release was observed at 8 and 16 hours.Generally equivalent at 23 hours. For SEFA ash: Observed similar effectas Venture ash in 3 cements. Holcim was behind at the early ages andequivalent at 23 hours.

The greater energy release detected by calorimetry in the carbonatedsamples indicates probable early strength increase. This is important inSCM mixes, because producers in many markets stop using fly ash or slagduring colder weather due to slower strength development.

Greater strength increases for the carbonated batches allows producersto use fly ash or slag in colder weather when slower strengthdevelopment associated with SCMs would otherwise cause them to optagainst using fly ash or slag.

This example demonstrates the use of low dose carbonation to acceleratestrength development in concrete mixes utilizing an SCM, thuspotentially partially or completely offsetting the retardation ofstrength development seen in these mixes when they are not carbonated.

Example 36

In this example the effects of low dose carbonation on reversing theretardation of early strength development in concretes containing anSCM, in this case, fly ash, was further studied.

One fly ash was used, Class F Trenton fly ash. Two ordinary portlandcements were used, St Mary's Bowmanville (STMB) and Roanoake. The blendfraction was 80% cement, 20% fly ash

The procedure was as follows:

-   -   Combine 1350 g of sand and 267.5 g of water in bowl and for mix        30 s    -   Add 428 g of cement 107 g of fly ash and mix for 30 s    -   For carbonated mortar, mix an additional 2, 4 or 6 minutes with        a CO₂ flow rate of 0.15 LPM    -   For control mortar mix an additional 4 minutes    -   Cast samples

The batch was then sampled and calorimetry performed as describedherein. Values derived from calorimetry were used as an alternativemarker to strength development, also as described herein.

The calorimetry results for the Roanoake-Trenton blend are shown inFIGS. 110 (power) and 111 (energy) and in Table 38 (energy relative tocontrol). The results for STMB cement are shown in FIGS. 112 (power) and113 (energy) and in Table 39 (energy relative to control).

TABLE 38 Energy, via calorimetry, relative to control at specific timeintervals for an 80/20 blend of Roanoake cement and Trenton fly ash TimeAfter Mixing (h) Control CO₂ 2 min CO₂ 4 min CO₂ 6 min 1 — — — — 2 100%49% 73% 67% 3 100% 74% 95% 86% 4 100% 90% 113% 99% 5 100% 103% 126% 107%6 100% 112% 130% 109% 7 100% 117% 130% 107% 8 100% 120% 127% 105% 9 100%121% 125% 102% 10 100% 121% 122% 100% 11 100% 120% 120% 99% 12 100% 120%117% 98% 13 100% 119% 114% 97% 14 100% 117% 112% 96% 15 100% 116% 110%96% 16 100% 115% 108% 96% 17 100% 114% 107% 96% 18 100% 114% 106% 96% 19100% 113% 105% 96% 20 100% 112% 104% 96% 21 100% 112% 104% 96% 22 100%112% 103% 96% 23 100% 111% 103% 96% 24 100% 111% 102% 97%

TABLE 39 Energy, via calorimetry, relative to control at specific timeintervals for an 80/20 blend of St Mary' s Bowmanville cement andTrenton fly ash Time After Mixing (h) Control CO₂ 2 min CO₂ 4 min CO₂ 6min 1 — — — — 2 100% 80% 68% 48% 3 100% 83% 81% 73% 4 100% 88% 88% 83% 5100% 94% 93% 89% 6 100% 98% 95% 91% 7 100% 100% 95% 90% 8 100% 101% 94%88% 9 100% 101% 92% 87% 10 100% 101% 92% 86% 11 100% 100% 91% 85% 12100% 100% 91% 85% 13 100% 99% 90% 84% 14 100% 99% 90% 83% 15 100% 98%89% 83% 16 100% 98% 89% 82% 17 100% 97% 89% 82% 18 100% 97% 89% 82% 19100% 96% 89% 82% 20 100% 96% 89% 82% 21 100% 96% 89% 82% 22 100% 95% 89%82% 23 100% 95% 89% 82% 24 100% 95% 89% 82%

There was strong acceleration observed in the Roanoake-Trenton blend.The 2 min dose (0.06% bwc CO₂ uptake) saw more energy released than thecontrol at ages beyond 5 hours, with at least 20% more energy observedthrough the interval of 8 to 12 hours. Total energy released at 24 hourswas 111% of the control. The 4 min dose (0.26% bwc CO₂ uptake) saw moreenergy released than the control at all times greater than 4 hours withthe benefit exceeding 10% from 6 hours to 15 hours. The maximum reached30% more at 6 to 7 hours. Total energy released at 24 hours was 102% ofthe control. The 6 min dose (0.38% bwc CO₂ uptake) released slightlymore energy that the control through the ages 5 to 9 hours (max 9% aheadat 6 hours). Total energy released at 24 hours was 97% of the control.

In contrast, there was no acceleration observed in the St Mary's-Trentonblend. The 2 min dose (0.14% bwc CO₂ uptake) saw less energy releasedthan the control at all ages except the interval of 7 to 12 hours whenit was equivalent. Total energy released at 24 hours was 95% of thecontrol. The 4 min dose (0.27% bwc CO₂ uptake) saw less energy releasedthan the control at all ages. The maximum was 95% in the interval of 6to 7 hours. Total energy released at 24 hours was 89% of the control.The 6 min dose (0.48% bwc CO₂ uptake) saw less energy released than thecontrol at all ages. The maximum was 91% at 6 hours. Total energyreleased at 24 hours was 82% of the control.

This Example is a further demonstration of the effects of mix type onthe carbonation results, with markedly different results being obtaineddepending on the cement used in the mix—virtually no effect ofcarbonation in the STMB-Trenton mix, and a pronounced effect in theRoanoke-Trenton mix. The effect of carbonation in a given mix is beststudied in that mix; this may be especially important in cement/SCMblends, in which both the specific type of cement and the specific typeof SCM may contribute reactive species that influence the course and/oreffect of carbonation. This Example also illustrates that, with theproper cement/SCM mix, carbonation of the mix, e.g., with low doses ofcarbon dioxide, can accelerate the development of early strength, asindicated by calorimetry; in some cases the acceleration can be quitemarked, even at a relatively low dose of carbon dioxide. Finally, agiven mix may demonstrate different time courses of acceleration ofstrength development; this can be useful in certain field conditionswhen a particular operation is desired to be carried out at a particulartime after the mix is poured, e.g., removal of molds, finishing, and thelike, which require a certain strength of the concrete. Earlier times ofaccelerated strength development could be desired to, e.g., shorten thetime that the concrete is in the mold, while later times of acceleratedstrength development could be desired to, e.g., allow concrete finishingto occur earlier.

Example 37

In this Example the use of bicarbonate as a source of carbonate in thecarbonation of cement mixes was studied.

As described elsewhere herein, and without being bound by theory, therelevant reactions in carbonation of cement mixes or other mixescontaining the requisite reactive species are:

-   -   1. Dissolution of gas in water to form dissolved carbon dioxide:

CO₂(g)→CO₂(solution)

-   -   2. Reaction of dissolved carbon dioxide with water to form        carbonic acid:

H₂O+CO₂(solution)→H₂CO₃(aq)

-   -   3. Reaction of carbonic acid with hydroxide or other base to        form bicarbonate:

H₂CO₃(aq)+OH⁻(aq)→HCO₃ ⁻(aq)+H₂O(l)

-   -   4. Reaction of bicarbonate with hydroxide or other base to form        carbonate:

HCO₃ ⁻(aq)+OH⁻(aq)→CO₃ ²⁻(aq)+H₂O(l)

-   -   5. Reaction of carbonate with calcium (or alternative ion) to        form solid carbonate:

CO₃ ²⁻(aq)+Ca²⁺(aq)→CaCO₃(s)

There are a number of points where the conditions under which thereactions are taking place can affect various steps in the carbonation.The dissolution of carbon dioxide in water, 1, is affected bytemperature, the presence or absence of catalysts, and other factors.Similarly, the formation of carbonic acid, 2, is affected by the pH ofthe water, etc., as is the reaction of carbonic acid with hydroxide orother base to form bicarbonate, 3. The base for the reaction of 3 neednot be a strong base, as the pK_(a) for this reaction is relatively low,around 7 or so, so that the reaction could be occurring even in the mixwater in embodiments in which carbon dioxide is added to the mix water.The processes of 1 and 2 may be circumvented by using carbondioxide-charged water (e.g., mix water) in a test; depending on the pHof the mix water, process 3 may also be partially or completelycircumvented as well. The use of bicarbonate solution does circumventall of processes 1, 2, and 3, allowing just carbonation of the cementmix to be tested.

In the present Example, a bicarbonate solution is used as a source ofsubstrate to be converted o carbonate in tests of carbonation of cementmixes. By removing the variables associated with dissolution andconversion to carbonic acid and bicarbonate, just the effects of thecement and other reactive components of the mix may be analyzed, to geta rapid and accurate picture of cement and other effects alone. It ispossible to determine whether or not carbonation is effective with agiven cement or cement mix, and to determine the optimum or desiredlevel of carbonation to be achieved, since all or substantially all ofthe bicarbonate is converted to carbonate in the reactions in the mixingcement mix. The effects of various doses on the timing of strengthincrease can also be observed. In this way, the focus in the field canbe shifted to achieving the desired carbonation, given the conditions ofmix water, mix time, timing of batch operations, source of carbondioxide, potential feedback control, and the like, to achieve consistentand efficient carbonation in the field. Lab results can be used inpreliminary field test to confirm the carbonation dose and todemonstrate the effectiveness of carbonation, before relying on deliveryof carbon dioxide to the cement mix in the field.

Where one CO₂ molecule forms a single bicarbonate molecule, an effectiveCO₂ dose as sodium bicarbonate can be calculated as follows:

CO₂(as bicarb)=(dose CO₂)*(Molar Mass Sodium Bicarbonate/Molar Mass CO₂)

-   -   Thus: CO₂ (as bicarb)=(dose CO₂)*(84/44)=(dose CO₂)*1.91    -   For example, a 0.10% bwc CO₂ dose would require a 0.191% bwc        dose of sodium bicarbonate

Two different cements were used in the tests, Lafarge Brookfield (LAFB)and St Mary's Bowmanville (STMB), with the batch plan shown in Table 40

TABLE 40 Dosage plan for bicarbonate testing Mass Mass Dosage EquivalentTotal Cement Water 1 Water 2 NaHCO₃ NAHCO₃ CO₂ dose Water Mass Batch (g)(g) (g) (g) (% bwc) (bwc) (g) 1 535 53.5 250 0 — — 303.5 2 535 53.5 2500.5 0.09% 0.05% 303.5 3 535 53.5 250 1.0 0.18% 0.10% 303.5 4 535 53.5250 2.0 0.37% 0.20% 303.5

The mix procedure was as follows:

-   -   Add sodium bicarbonate (NaHCO₃) into water 2 and stir thoroughly        to dissolve    -   Combine sand and water 1 (10% of cement mass) in bowl and mix 30        s    -   Add cement to bowl and mix 30 s    -   Add water 2 over designated timeframe (4 minutes)    -   Mix an additional 30 s

The batch was then sampled and calorimetry performed as describedherein. Values derived from calorimetry were used as an alternativemarker to strength development, also as described herein.

The results for STMB cement are shown in FIGS. 114 (power) and 115(energy) and in Table 41 (energy relative to control). The results forLAFB cement are shown in FIGS. 116 (power) and 117 (energy) and in Table42 (energy relative to control).

TABLE 41 Energy, via calorimetry, relative to control at specific timeintervals for STMB cement mixed with sodium bicarbonate Time After 0.09%0.18% 0.37% Mixing (h) Control bicarb bicarb bicarb 1 — — — — 2 100% 95%116% 100% 3 100% 99% 104% 102% 4 100% 101% 104% 102% 5 100% 103% 104%101% 6 100% 103% 103% 98% 7 100% 103% 103% 97% 8 100% 103% 102% 95% 9100% 103% 101% 94% 10 100% 103% 101% 94% 11 100% 103% 101% 94% 12 100%103% 101% 94% 13 100% 103% 101% 94% 14 100% 103% 101% 94% 15 100% 103%101% 94%

TABLE 42 Energy, via calorimetry, relative to control at specific timeintervals for LAFB cement mixed with sodium bicarbonate Time After 0.09%0.18% 0.37% Mixing (h) Control bicarb bicarb bicarb 1 — — — — 2 100% 92%141% 163% 3 100% 95% 133% 155% 4 100% 103% 134% 151% 5 100% 107% 130%140% 6 100% 109% 123% 129% 7 100% 108% 116% 120% 8 100% 106% 110% 112% 9100% 105% 106% 107% 10 100% 104% 103% 104% 11 100% 103% 100% 101% 12100% 102% 98% 98% 13 100% 100% 96% 96% 14 100% 99% 94% 95% 15 100% 99%93% 94% 16 100% 98% 92% 93% 17 100% 98% 92% 92% 18 100% 97% 91% 91% 19100% 97% 90% 91% 20 100% 96% 90% 90%

The results confirm those of previous Examples that show that theeffects of carbonation are highly dependent on cement type used. In thebatches in which STMB cement was used, the bicarbonate had almost noeffect on the calorimetry, at any dose, whereas in the LAFB batches,carbonation at all doses caused an increase in early hydration, similarto Example 33, with the effect being dose-dependent. 2.0 g ofbicarbonate was the best of three doses with a 63% increase in energy attwo hours gradually declining to 12% at 8 hours.

This Example demonstrates the use of bicarbonate in testing ofcarbonation of different cement mixes, in order to examine effects ofcarbonation alone, without dissolution and early reaction effects, anddemonstrates that different cements react differently to carbonation.The results of the use of bicarbonate with the LAFB and STMB cementswere in agreement with results from carbonation using carbon dioxidewith these cements, confirming that bicarbonate can be used as acarbonation testing tool.

Example 38

In this Example, carbonated mix water was used as the source of carbondioxide for carbonation of cement mixes, and the effects of delaying theaddition of the carbonated mix water, or duration of addition of thecarbonated mix water were tested.

In a first test, carbonated mix water was added at the beginning ofmixing or after a short delay. This allows the testing to concern itselfwith timing of the CO₂ in the mixing process rather than with agas-to-solution reaction, i.e., to circumvent reactions 1 and 2 shown inExample 37 Carbonated water was Perrier.

The mix procedure was as follows:

-   -   Combine sand, tap water 1 (53.5 g), carbonated water 1 (either        no carbonation or carbonated) and cement in bowl—mix 60 s    -   Add both tap water 2 and carbonated water 2 (carbonated) to bowl        over 10 s—mix 60 s    -   Mix mortar for an additional 1 min    -   Cast for strength, CO₂ and calorimetry

The batch plan was as shown in Table 43.

TABLE 43 Carbonated timing work batches Tap Carb Tap Carb. Total CementWater 1 Water 1 Water 2 Water 2 pre- Batch (g) (g) (g) (g) (g) wet 1 535267.5 0 0 0 267.5 2 535 53.5 0 214 0 53.5 3 535 53.5 214 0 0 267.5 4 53553.5 0 0 214 53.5

The batch was then sampled and calorimetry performed as describedherein. Values derived from calorimetry were used, also as describedherein.

The results for STMB cement are shown in FIGS. 118 (power) and 119(energy) and in Table 44 (energy relative to control). The results forLAFB cement are shown in FIGS. 120 (power) and 121 (energy) and in Table45 (energy relative to control).

TABLE 44 Energy, via calorimetry, relative to control at specific timeintervals for STMB cement subjected to different mix water compositionsand timings. Time After Control - CO2 up CO2 - split Mixing (h) Controlsplit water front water 2 100% 94% 0% 134% 3 100% 103% 37% 122% 4 100%103% 46% 124% 5 100% 103% 54% 125% 6 100% 103% 62% 123% 7 100% 103% 70%119% 8 100% 103% 76% 116% 9 100% 103% 81% 112% 10 100% 103% 85% 110% 11100% 103% 88% 108% 12 100% 103% 90% 106% 13 100% 103% 91% 104% 14 100%103% 92% 103% 15 100% 103% 93% 101% 16 100% 103% 93% 100% 17 100% 103%94% 99% 18 100% 103% 94% 98% 19 100% 103% 94% 97%

TABLE 45 Energy, via calorimetry, relative to control at specific timeintervals for LAFB cement subjected to different mix water compositionsand timings. Time After Control - CO2 up CO2 - split Mixing (h) Controlsplit water front water 2 100% 227% 0% 41% 3 100% 137% 51% 94% 4 100%122% 53% 107% 5 100% 117% 65% 115% 6 100% 114% 75% 115% 7 100% 112% 82%111% 8 100% 110% 88% 107% 9 100% 109% 92% 104% 10 100% 108% 95% 102% 11100% 107% 98% 100% 12 100% 107% 101% 98% 13 100% 106% 103% 97% 14 100%106% 104% 96% 15 100% 106% 105% 95% 16 100% 106% 106% 95% 17 100% 106%107% 95% 18 100% 106% 107% 95% 19 100% 106% 108% 95% 20 100% 106% 108%95% 21 100% 106% 108% 95% 22 100% 106% 108% 94% 23 100% 106% 108% 94%

For the STMB cement, the addition of carbonated water as part of the mixwater showed a retardation up to 10 hours (less than 85% of the energyreleased by the control) before reaching 93% of the energy released bythe control at ages greater than 15 hours. In contrast, the delayedaddition of the same amount of mix water showed that energy release wasmore than 15% ahead of the control through the first 8 hours ofhydration before being equivalent to the control after 15 hours. Therewas no appreciable difference in the uncarbonated system whether thewater was added all at once or in an 80/20 split.

For the LAFB cement the addition of carbonated water as part of the mixwater showed a retardation across the first 7 hours (wherein less than85% of the energy released by the control) before reaching an 8%increase in energy released versus the control at ages greater than 19hours. For the delayed addition of the same amount of carbonated waterthe hydration energy release was more than 15% ahead of the control bythe 5^(th) and 6^(th) hours of hydration before being slightly behindthe control after 15 hours. In this case, the 80/20 split addition ofuncarbonated mix water showed a marked acceleration at early timepoints, as compared to the all at once addition.

These results demonstrate again that results vary depending on thecement used. Both the STMB and the LAFB showed a marked retardation ofhydration, as shown by calorimetry, when the carbonated mix water wasadded without a delay; however, the LAFB cement had recovered and evenaccelerated hydration by 12 hours, whereas the STMB did not recover inthe 23 hours tested. In both STMB and LAFB, delaying the addition of thecarbonated mix water resulted in acceleration of hydration, but atdifferent times and to different degrees. For STMB, there was markedacceleration at the first hour time point, continuing to 15 hours. Incontrast, the acceleration of hydration in the LAFB system was notapparent until 4 hours and ended by 11 hours, and was moderate comparedto that of STMB.

In a second test, the delay until addition of carbonated water and theamount of carbonated water were kept constant, and the overall durationof addition of the water was varied. LAFB cement was used. Thecarbonated water was Perrier. The mix procedure was as follows:

-   -   Combine sand and water 1 in bowl—mix 30 s    -   Add cement to bowl—mix 30 s    -   Add both water 2 and carbonated water over designated timeframe        (2-5 minutes)    -   Mix mortar for total of 2 minutes    -   Note for batches 4 and 5 the total mix time was 5 minutes

The batch plan was as shown in Table 46.

TABLE 46 Batch plan for various durations for addition of carbonatedwater. Mass Carbonated Total Cement Water 1 water Dose Water AdditionBatch (g) (g) (g) Mass (g) time 1 535 53.5 250 303.5  30 seconds 2 53553.5 250 303.5  60 seconds 3 535 53.5 250 303.5 120 seconds 4 535 53.5250 303.5 180 seconds 5 535 53.5 250 303.5 300 seconds

The calorimetry results are shown in FIGS. 122 (power) and 123 (energy)and in Table 47 (energy relative to control).

TABLE 47 Energy, via calorimetry, relative to control at specific timeintervals for LAFB cement with different durations of time forcarbonated water addition Time After Mixing (h) 0.5 min 1 min 2 min 3min 5 min 1 — — — — — 2 — — — — — 3 100% 109% 122% 186% 228% 4 100% 117%141% 192% 229% 5 100% 116% 137% 166% 191% 6 100% 111% 125% 140% 156% 7100% 107% 117% 124% 135% 8 100% 104% 112% 114% 122% 9 100% 102% 109%108% 114% 10 100% 101% 107% 104% 109% 11 100% 101% 106% 102% 106% 12100% 100% 105% 100% 104% 13 100% 100% 104% 99% 102% 14 100% 99% 104% 98%101% 15 100% 99% 103% 97% 100% 16 100% 99% 103% 97% 100% 17 100% 99%102% 97% 99%

As compared to the quickest addition of carbonated water, the slower theaddition the greater the benefit. Benefits were observed mostly inhydration periods up to 9 hours after mixing.

This Example demonstrates that varying the duration of addition ofcarbonated mix water to a cement mix can have marked effects on earlyhydration.

Example 39

In this Example, carbonated mix water was derived from artificial washwater and used as the source of carbon dioxide for carbonation of cementmixes.

In concrete production, process water is produced in various stages ofthe production and packaging process, such as truck cleanout and otherprocesses, where the process water has a high pH that can be necessaryto reduce before the water can be discharged. Current treatment methodsinclude the use of HCl, but the process is difficult to control and hassafety issues involved with handling a concentrated acid. An alternativemethod utilizes carbon dioxide addition to the process water. The carbondioxide forms carbonic acid, a weak acid, that is converted tobicarbonate and ultimately carbonate (e.g., calcium carbonate). As thepH is lowered by these reactions, it eventually reaches 7 or 8, and theprecipitated calcium carbonate dissolves, creating calcium bicarbonate.Because of the pKas of the various reactions, the system is buffered andit is easier to achieve the desired pH for discharge. Thus, certainembodiments provide treatment of process water from a manufacturingprocess that produces high-pH process water, such as concretemanufacture, with carbon dioxide, such as carbon dioxide produced inlime and/or cement manufacture to lower the pH of the process water.This Example tests whether the carbonated wash water could then be usedas mix water in the concrete batching process.

The following procedure was used:

-   -   A synthetic “wash water” was prepared by mixing a 2% cement by        weight solution with 0.20% bwc sodium gluconate, in water. The        gluconate was added since the addition of a retarder is a        conventional part of the wash process to prevent the concrete        from setting up in the ready-mix truck prior to washing.    -   The mixture was shaken periodically and allowed to sit for 24        hr.    -   Combine sand (1350 g) and water 1—mix 30 s    -   Add cement (STMB, 535 g)—mix 30 s    -   Add both water 2 and wash water to bowl—mix 2 minutes    -   Cast samples

The testing compared unfiltered vs filtered wash water, in bothuncarbonated and carbonated variations. Wash water was carbonated bytreating it in a home soda making device according to the manufacturer'sinstructions to make carbonated water. The wash water was filteredthrough filter paper to remove suspended solids. Batching is shown inTable 48. The carbonated wash water represented over 60% of the totalwater used in the cement mixes.

TABLE 48 Carbonated wash water work batches Wash Total Cement Water 1Water Water 2 Water Wash Batch (g) (g) (g) (g) (g) water 1 535 53.5171.2 42.8 267.5 Filtered, uncarbonated 2 535 53.5 171.2 42.8 267.5Filtered, carbonated 5 535 53.5 171.2 42.8 267.5 Unfiltered,uncarbonated 6 535 53.5 171.2 42.8 267.5 Unfiltered, carbonated

The calorimetry results are shown in FIGS. 123 (power) and 124 (energy)and in Tables 49 (unfiltered) and 50 (filtered).

TABLE 49 Energy, via calorimetry, relative to uncarbonated control atspecific time intervals for STMB cement with filtered simulated washwater used as 80% of the mix water Time After Filtered, Filtered, Mixing(h) uncarbonated carbonated 2 100% 194% 3 100% 110% 4 100% 111% 5 100%109% 6 100% 109% 7 100% 108% 8 100% 107% 9 100% 105% 10 100% 103% 11100% 102% 12 100% 101% 13 100% 100% 14 100% 99% 15 100% 98% 16 100% 96%17 100% 96% 18 100% 95%

TABLE 50 Energy, via calorimetry, relative to uncarbonated control atspecific time intervals for STMB cement with unfiltered simulated washwater used as 80% of the mix water Time After Unfiltered, Unfiltered,Mixing (h) uncarbonated carbonated 2 100% 28% 3 100% 62% 4 100% 77% 5100% 88% 6 100% 95% 7 100% 99% 8 100% 101% 9 100% 102% 10 100% 103% 11100% 103% 12 100% 104% 13 100% 103% 14 100% 103% 15 100% 103% 16 100%102% 17 100% 102% 18 100% 102%

When the wash water was filtered the carbonation treatment resulted insome early hydration acceleration (94% more energy released through 2hours, 10% through 3 hours, 11% through 4 hours) before trendingdownwards to be 8% lower at 22 hours. When the wash water was unfilteredthe carbonation treatment resulted in early hydration retardation (notuntil 6 hours was the energy within 10% of the control) before theenergy release became comparable to the control.

This Example illustrates that carbonated wash water can be used as partor all of the mix water in a cement mix with acceleration of hydrationin the subsequent mix compared to uncarbonated control. The use ofcarbonated wash water can allow the simultaneous treatment of the washwater, its disposal in a cement mx, and a beneficial or at least neutraleffect on the subsequent mix. If the carbon dioxide comes from thecement making process itself, it also represents an avenue fordecreasing the carbon footprint of the overall cement process.

Example 40

In this Example, the effect of carbonation on early hydration was testedfor two different low temperature conditions.

Industrially produced concrete can vary in temperature, both at thebatching facility and at the job site. Typically, a concrete mix isrequired to be between 10−30° C. at time of delivery, though it canpotentially be hotter or colder at time of batching

In this test, a series of mortar samples were carbonated at lowtemperatures to observe if the effect of CO₂ on cement was sensitive tomix temperature. Two temperature ranges were used, 5 to 10° C. and 10 to15° C. Isothermal calorimetry was performed in the same temperaturerange as mixing.

The procedure was as follows:

-   -   Combine 1350 g of sand and 267.5 g of water in bowl and for mix        30 s    -   Add 535 g of cement and mix for 30 s    -   For carbonated mortar, mix an additional 2, 4 or 6 minutes with        a CO₂ flow rate of    -   0.15 LPM    -   For control mortar mix an additional 4 minutes    -   Cast samples

Two ordinary portland cements were used: St Mary's Bowmanville (STMB) orLafarge Brookfield (LAFB)

For LAFB cement mortars, FIGS. 125 and 126 show power and energy curves,respectively at 5 to 10° C., and FIGS. 127 and 128 and show power andenergy curves, respectively at 10 to 15° C., while Table 51 showssummary of energy compared to control system at 5 to 10° C. and Table 52shows summary of energy compared to control system at 10 to 15° C.

TABLE 51 Energy, via calorimetry, relative to control at specific timeintervals for LAFB cement hydrated at a temperature between 5 and 10° C.Time After Mixing Control (h) 5° C. CO2 2 min CO2 4 min CO2 6 min 1 — —— — 2 100% 80% 45% 22% 3 100% 73% 46% 38% 4 100% 73% 40% 35% 5 100% 75%45% 41% 6 100% 78% 57% 53% 7 100% 80% 69% 64% 8 100% 83% 79% 74% 9 100%85% 86% 81% 10 100% 88% 92% 86% 11 100% 89% 95% 90% 12 100% 90% 99% 93%13 100% 91% 102% 96% 14 100% 92% 104% 98% 15 100% 93% 106% 100% 16 100%93% 107% 101% 17 100% 94% 109% 102% 18 100% 94% 110% 103% 19 100% 94%110% 103% 20 100% 94% 111% 104% 21 100% 95% 111% 104% 22 100% 95% — — 23— — — — 24 — — — —

TABLE 51 Energy, via calorimetry, relative to control at specific timeintervals for LAFB cement hydrated at a temperature between 10 and 15°C. Time After Mixing Control (h) 10° C. CO2 2 min CO2 4 min CO2 6 min 1100% 106% 160% 0% 2 100% 84% 108% 36% 3 100% 82% 95% 73% 4 100% 89% 102%97% 5 100% 95% 107% 107% 6 100% 97% 107% 107% 7 100% 99% 105% 104% 8100% 100% 102% 100% 9 100% 100% 101% 98% 10 100% 100% 99% 95% 11 100%100% 97% 93% 12 100% 100% 95% 91% 13 100% 100% 94% 89% 14 100% 99% 92%88% 15 100% 99% 92% 87% 16 100% 99% 91% 86% 17 100% 99% 90% 86% 18 100%98% 90% 85% 19 100% 98% 89% 85% 20 100% 98% 89% 84% 21 100% 98% 88% 84%22 100% 98% 88% 84% 23 100% 97% 88% 83% 24 100% 97% 87% —

For STMB cement mortars, FIGS. 129 and 130 show power and energy curves,respectively at 5 to 10° C., and FIGS. 131 and 132 and show power andenergy curves, respectively at 10 to 15° C., while Table 53 showssummary of energy compared to control system at 5 to 10° C. and Table 54shows summary of energy compared to control system at 10 to 15° C.

TABLE 53 Energy, via calorimetry, relative to control at specific timeintervals for STMB cement hydrated at a temperature between 5 and 10° C.Time After Mixing Control (h) 5° C. CO2 2 min CO2 4 min CO2 6 min 1 — —— — 2 100% 62% 67% 76% 3 100% 56% 64% 68% 4 100% 57% 67% 74% 5 100% 60%72% 83% 6 100% 64% 78% 91% 7 100% 68% 83% 97% 8 100% 72% 88% 100% 9 100%75% 91% 102% 10 100% 79% 93% 103% 11 100% 82% 95% 103% 12 100% 84% 96%103% 13 100% 86% 97% 102% 14 100% 88% 98% 102% 15 100% 89% 99% 102% 16100% 90% 100% 102% 17 100% 92% 101% 102% 18 100% 93% 102% 103% 19 100%94% 103% 103% 20 100% 95% 104% 103% 21 100% 96% 105% 103% 22 100% 96%105% 103% 23 100% 97% — — 24 — — — —

TABLE 54 Energy, via calorimetry, relative to control at specific timeintervals for STMB cement hydrated at a temperature between 10 and 15°C. Time After Mixing Control (h) 10° C. CO2 2 min CO2 4 min CO2 6 min 1— — — — 2 100% 26% 47% 61% 3 100% 54% 80% 87% 4 100% 67% 100% 103% 5100% 75% 109% 110% 6 100% 80% 112% 111% 7 100% 83% 112% 109% 8 100% 85%109% 106% 9 100% 88% 107% 104% 10 100% 90% 106% 103% 11 100% 92% 105%102% 12 100% 93% 104% 101% 13 100% 94% 103% 100% 14 100% 94% 102% 99% 15100% 94% 100% 98% 16 100% 95% 99% 98% 17 100% 95% 99% 98% 18 100% 95%98% 97% 19 100% 96% 98% 97% 20 100% 96% 97% 97% 21 100% 96% 97% 97% 22100% 96% 96% 97% 23 100% 96% 96% 97% 24 100% 97% 96% 97%

For the LAFB mortar, at both temperatures, the middle (4 min) doseproduced the greatest enhancement of hydration, and at both temperaturesthe effect started earlier than the effect for the highest dose (6 min);in the 10 to 15 temperature, there was already a 60% increase inhydration at the one hour time point for the 4 min dose of carbondioxide. For the STMB mortar, the middle and high doses produced roughlyequivalent moderate increases in hydration at both temperatures, but thestart of the effect was markedly different for the two doses at thelower temperature, beginning at about 9 hours for the 6 min dose and at17 hours for the 4 min. dose.

This Example demonstrates that carbonation of a cement mix can have aneffect on early strength development in concretes to be batched and usedat low temperatures, and that the optimal dose can be temperature- andcement type-dependent. In addition, the timing of onset of increasedstrength development can be manipulated by manipulating the dose in somecircumstances.

Example 41

This Example demonstrates the in situ formation of nanocrystals ofcalcium carbonate under specific carbonation conditions in cement.

Oil Well Cement

Laboratory scale experiments were performed on a model system in orderto better understand the impacts of the carbon dioxide. The testing usedoil well cement due to its low initial calcite content (below detectionlimits on XRD). Therefore small quantities of carbonate reaction productdevelopment could be readily distinguished.

Samples were generated by mixing 250 g of water with 500 g of untreatedoil well cement in a blender for 30 seconds. The blender was floodedwith continuous supply of 100% CO₂ gas for a one minute during blending.Samples were flash frozen with liquid nitrogen following the mixingperiod and then freeze dried to arrest the hydration and carbonationreactions. The early hydration was examined by sampling the batch atfive distinct times (t=immediately after the end of mixing, 5 minutes, 4hours, 10 hours, and 24 hours after the end of mixing). A parallel setof samples for an uncarbonated (control) system were also prepared.Quantitative X-ray Diffraction (QXRD) was employed to characterize theconstituents of the prepared samples. Total inorganic carbon was used toquantify the carbon dioxide.

GU Cement

An investigation was conducted to characterize the carbonate reactionproducts through carbonation of a simple cement system. A high degree ofcarbonation was achieved to allow for direct observation of thecrystalline reaction products.

The experiment mixed 450 g of GU cement and 50 g of distilled deionizedwater in an airtight, resealable plastic bag. The materials werehand-agitated through the bag until homogenously blended and the cementwas moistened (30 seconds). The bag was inflated with 100% CO₂ gas andsealed. The system was allowed to react until all of the carbon dioxidehad reacted (over several minutes) and the bag had deflated. Thisprocess was repeated a total of ten times over the course of 1 hour. Aseparate bag was prepared identically, but no carbon dioxide gas wasadded into the plastic bag. Carbonate content was quantified by QXRD andthe microstructure was imaged using SEM.

Oil Well Cement QXRD Results

The QXRD results of the oil well cement samples are summarized in Table55 (hydrated samples) and Table 56 (carbonated series). Results arepresented as percentage mass fraction per normalized starting mass.Statistical analysis of the data collected through QXRD suggested thatthe percentage error is controlled by analytical error. An equationrepresenting this distribution was used to calculate all errors based onabsolute abundance. The developments of C3S, calcite, ettringite,calcium hydroxide, and amorphous content were tracked. The Rietveldidentification of amorphous content was interpreted, in part, torepresent C—S—H gel. While the amorphous content of the anhydroussamples would not adhere to this interpretation, the C—S—H developmentwould generally be associated with the net increase in amorphous contentas hydration proceeds.

TABLE 55 Phase Abundance Summary (wt %) via QXRD for hydrated oil wellcement series Phase Anhydrous 0 min 5 min 4 hours 10 hours 24 hours C3S54.9 ± 1.2  54.5 ± 1.2 53.4 ± 1.2  49.9 ± 1.2 46.0 ± 1.2  26.4 ± 1.0 Calcite n/d n/d n/d n/d 0.9 ± 0.4 1.0 ± 0.4 Amorphous 8.6 ± 0.7 8.39 ±0.7 7.6 ± 0.7 13.5 ± 0.8 20.0 ± 0.9  34.1 ± 1.1  Ettringite 0.6 ± 0.3 0.7 ± 0.4 1.1 ± 0.4  1.4 ± 0.4 1.8 ± 0.5 4.4 ± 0.6 Gyspum 4.0 ± 0.6 3.3 ± 0.6 4.5 ± 0.6  3.6 ± 0.6 3.3 ± 0.6 0.9 ± 0.4 Ca(OH)₂ n/d n/d n/dn/d n/d 6.0 ± 0.7

TABLE 56 Phase Abundance Summary (wt %) via QXRD for carbonated oil wellcement series Phase Anhydrous 0 min 5 min 4 hours 10 hours 24 hours C3S54.9 ± 1.2  53.7 ± 1.2  52.3 ± 1.2  51.6 ± 1.2  42.3 ± 1.1  27.9 ± 1.0 Calcite n/d 0.8 ± 0.4 0.5 ± 0.3 1.0 ± 0.4 1.5 ± 0.4 2.8 ± 0.5 Amorphous8.6 ± 0.7 10.4 ± 0.8  11.2 ± 0.8  13.0 ± 0.8  25.4 ± 1.0  38.3 ± 1.1 Ettringite 0.6 ± 0.3 0.6 ± 0.3 0.5 ± 0.3 0.7 ± 0.4 1.1 ± 0.4 2.5 ± 0.5Gypsum 4.0 ± 0.6 4.1 ± 0.6 4.5 ± 0.6 4.3 ± 0.6 3.0 ± 0.6 n/d Ca(OH)₂ n/dn/d n/d n/d 1.0 ± 0.4 5.2 ± 0.6

The progress of C3S dissolution and reaction is monitored by the changein its relative abundance (decrease) with time. The carbonated case isshown to be parallel the hydrated case wherein the two values areequivalent within the range of error at the initial measurement, 5minutes and 4 hours. A greater amount C3S has reacted in the carbonatedsample (potentially 8% more) at 10 hours but by 24 hours the C3S in thetwo conditions is again functionally equivalent. The carbon dioxide isshown to only have a small effect on the overall C3 S dissolution orreaction kinetics given that that total reaction of C3 S was largely thesame. The increased reaction of C3 S in the carbonated oil well cementat 10 hours as observed by the QXRD agreed with the field ready-mixconcrete calorimetry (previous Examples) wherein greater energy wasreleased in the 7 to 11 hour interval. This stage of hydration isassociated with the end of the acceleration period when the initialsilicate hydration starts to slow down. It is possible that thecarbonate reaction products are providing a seeding role to boost thehydration or are otherwise affecting the kinetics of the hydrationreaction.

Initial concentrations of calcite in the anhydrous cement were belowdetection limits. Calcite appears in the hydrated system after 600 minat a level of 0.90±0.40%. It was unchanged through to the end of theanalysis. The large relative error (44%) is due to the uncertainty atsuch low concentrations of calcite. In the carbonated sample an increasecalcite concentration is observed immediately following the carbondioxide gas injection 0.80±0.37% by weight calcite. This level ofcalcite remains relatively constant in the system through the first 4hours. In the sample at 10 hours the concentration of calcite increasesto 1.52±0.45% by weight before ultimately reaching its maximum observedconcentration of 2.83±0.55% at 24 hours. The amount of calcite in thesystem appears to increase but it is recognized that no additionalcarbon dioxide was added to the system after the initial mixing. Theobserved increase with time is likely attributable to the calcitereaction products initially being poorly crystalline or too small(xrd-invisible) before developing increased crystallinity or sizewherein they could be detected through xrd.

The amorphous content of the carbonated sample is 24% higher than thatof the hydrated control immediately after carbonation. At 5 minutes itis 47% greater. It fell 4% behind at 4 hours before accelerating to 27%ahead at 10 hours and 12% ahead at 24 hours. The small lag at 4 hourswas mirrored by the C3 S content whose consumption was shown to beslightly less for the carbonated paste at 4 hours. The amorphouscontent, as it would parallel C—S—H content and taken as a proxy forhydration progress, mirrors some of the field observations. The fieldcalorimetry provided evidence of a pivot wherein hydration was slightlybehind at 4 hours and notably ahead at 10 hours before showing astrength benefit at 24 hours.

The ettringite content of the carbonated paste was found to be lowerthan in the hydrated paste. If the quantification is considered as a netincrease over the trace found in the anhydrous state then the carbonatedpaste contained 90% less ettringite at 4 hours, 56% at 10 hours and 49%at 24 hours. The implication is that the ettringite was slower to formin the carbonated sample.

The gypsum content of both samples did not conclusively change throughthe four hour samples. The decrease, via consumption during hydration,was greater in the carbonated sample than the hydrated sample. Itappeared that all of the gypsum had been consumed in the carbonatedsample at 24 hours but less than 80% had reacted in the hydrated sample.

The first detection of calcium hydroxide was in the 10 hour sample, butonly in the carbonated paste. At 24 hours the carbonated sample had 88%of the portlandite that was detected in the control paste.

The small dose of carbon dioxide creates nano-calcite but does notprevent the conventional hydration reaction pathways from proceeding.The calcium silicates continue to hydrate, while portlandite andettringite continue to form.

Oil Well Cement Total Inorganic Carbon Analysis

Total Inorganic Carbon (TIC) measurements were conducted for the threestates (anhydrous, hydrated and carbonated). The analysis would accountfor carbon in amorphous nanoparticles of calcite that would beinsufficiently crystalline and/or too small to be observed through QXRD.

The TIC for the anhydrous cement was 0.098%. Upon the carbonationtreatment the carbon had increased to 0.264%. At the equivalent age thecarbon content of the hydrated sample was 0.097%. and unchanged from theanhydrous sample. The TIC data proves that carbon dioxide had enteredthe system even if the QXRD was only detecting some of the ultimatevalue. A net increase of 0.166% was observed. This represents 0.377% CO₂by weight of cement.

GU Cement SEM

The production of a heavily carbonated paste sample succeeded inincreasing the calcite content (normalized over the anhydrous state)from 6.7% in the anhydrous to 37.7% in the carbonated. Converting thecalcite in % CaCO₃ to % CO₂, shows that the carbonated sample had a netCO₂ content of 13.6% by weight of the anhydrous cement. This level ofcarbonation ensures that the reaction products are found in considerablygreater abundance than what is achieved in the industrial case.Nonetheless, it serves as an effective system for analysis given thatthe reaction products are easy to observe in a neat paste system thathas a high degree of reaction.

The electron microscopy of the carbonated sample (shown in themicrograph of FIG. 137) revealed that numerous rhombohedral nanocrystalswere present in the system. The primary dimension of the particlesgenerally exceeded 10 nm and was predominantly less than 150 nm. Thesizes of the particles were too small to allow for an effective directchemical assessment through EDS. However, the particle geometry isconsistent with calcite and the QXRD identified the presence of largeamounts of calcite so the conclusion is made that the carbonationprocess has achieved in situ formation of nano-crystalline calcite. Theproduction method (extensive and aggressive carbonation) resulted inreaction products that are likely in larger sizes and in greaterquantities than what would have been found in the industrial samples.

This Example revealed that the hydration pathways were broadly the samewith and without carbonation. The conventional hydration phases formedafter the carbonation reaction occurred. The impact of the carbonationmay have been to increase the formation of C—S—H in the 10 to 24 hourtimeframe. Nanocrystalline, homogeneously distributed calcium carbonatewas formed in situ in the process.

Example 42

This Example outlines a liquid CO₂ injection system, for example, toaccommodate dry batch ready mix plants for efficient delivery of CO₂into the concrete trucks and seamless installation of components. Thesystem applies to operations that utilize a loading boot to depositmaterials into the drum of a ready-mix truck; a loading boot isgenerally a flexible, enclosed shoot that can be positioned into thehopper of the ready-mix truck and guides materials into the drum of thetruck.

The system uses components in addition to the standard boot components.

Additional Component Descriptions:

-   -   Rigid pipe, e.g., steel pipe (for example, ID=2¼″)    -   Flexible hose, e.g., flexible rubber hose (for example, ID=1½″)    -   Vacuum jacketed hose (for example, ID=¾″)    -   5-port, 4-way air solenoid valve    -   Telescopic air cylinder rod    -   Plastic slider    -   ¾″ 90° FNPT swivel elbow    -   ¼″ Rubber air hose (×2)

The liquid CO₂ injection system includes a flexible hose, e.g., a rubberhose, housed in a steel pipe. The flexible hose may be made of anysuitable material that possesses sufficient flexibility for theoperations of the system, as well as the ability to withstand thetemperatures of the solid and gaseous carbon dioxide that pass throughit. The steel pipe is aligned so that it does not extend further thanthe bottom of the aggregate bin (see FIG. 135), however, the hoseextends through the loading boot and into the concrete truck's chutethrough the action of a telescopic air cylinder rod (or rotary device),or other device suitable for extending the hose, during injection. Onceextended into the chute of the concrete truck, the hose aligns itselfwith the central axis of the truck to maximize concrete CO₂ uptake, butnot so far as to be in contact with the destructive fins of the truck.

The steel pipe is installed directly above the loading boot and ismounted to, or near, the cement hopper. See FIG. 135 for an idea ofwhere the steel pipe should be mounted.

The pipe is positioned so that it is free of falling materials enteringthe truck through the loading boot. Inside the steel pipe is atelescopic air cylinder and rod that determines the position of theflexible hose. The rod is controlled by an air solenoid valve thatpermits the flow of air to the air cylinder at two separate ports, oneto retract the rod and the other to extend it. The rod is connected to aplastic slider that sits inside the steel pipe. A 90° female NPT swivelelbow is installed in the plastic slider that will be used to connectthe flow of CO₂ from the CO₂ supply system to the flexible rubber hose.A long slot is cut on the side of the steel pipe to allow the CO₂ lineto follow the rubber hose into its extended position. A vacuum jacketedhose is used from the elbow to ensure the CO₂ line connected to theplastic slider remains flexible even after injection. Due to the extremecold of liquid CO₂ a regular hydraulic line would freeze duringinjection and would become completely rigid. The vacuum jacketed hose isslightly longer than the distance the rubber hose must travel from itsretracted to extended position, after this a copper line or insulatedhydraulic hose is permitted to the CO₂ supply system.

The injection system can be controlled manually or by any suitablecontrol system, such as a direct logic system, as described below.

Direct Logic

The air solenoid valve has one input port and two output ports. Eachoutput port controls one end of the telescopic air cylinder and arewired to a single pole, double throw (SPDT) relay switch. When the relayswitch does not have power it permits the flow of air through the firstsolenoid valve output and keeps the air cylinder rod retracted. The usesends a continuous 120 VAC signal from their system to the injectionsystem to commence the injection sequence. Once the signal is receivedby the injection system the relay switch receives power, closes oneoutput port and opens the other. This causes air to flow through thesecond output on the air solenoid valve and allows the rod to extend. Adelay is used in the mix recipe to ensure CO₂ does not start injectinguntil the rod is completely extended and the flexible rubber hose is inits correct position inside the truck. At this point the injectionsystem begins permitting the flow of CO₂ through the system and into theconcrete truck. See FIG. 136 for a schematic of the air cylinder rodinside the steel pipe in its retracted and extended position. It shouldbe noted that rotary solenoids, or other suitable device, could also beused to extend the flexible rubber hose into the truck, e.g., if spaceis an issue. This design can be custom fitted to meet the requirementsfrom most if not all ready mix producers. Cleanliness permitting, theair solenoid valve can also be mounted outside of the steel pipe and runalongside it to reduce the length.

The user's system counts pulse signals that are sent from the injectionsystem that equate to a predetermined mass of CO₂. Once the requireddosage of CO₂ is achieved, the user ceases the continuous 120 VAC signaland the relay switch loses power. This causes the air cylinder rod toretract and remove the flexible hose from the concrete truck. Theinjection sequence is not complete until the rod is sufficientlyretracted to be out of the way of the trucks and falling materials. Thisis achieved by a visible message on the Human Machine Interface (HMI)screen when the retracted rod triggers a proximity sensor (or timedependent).

Injection Sequence

The air solenoid valve is triggered once all materials have passedthough the loading boot and into the concrete truck. It is typically thelast step in the batching sequence. The injection sequence is generallynot complete until the rod has been sufficiently retracted and out ofthe way of other materials entering the loading boot. At this time amessage will be displayed to the plant's batcher that loading iscomplete and the driver can leave from under the loading boot.

Typical injection sequence:

-   -   1. A concrete truck drives under the loading boot and receives        all of its materials (aggregate, cement, water, etc.)    -   2. The user sends a continuous 120 VAC signal to the injection        system once all materials have been loaded to commence the        injection of CO₂    -   3. The injection system uses a single pole, double throw (SPDT)        relay switch to control an air solenoid valve        -   a. When the relay switch is normally closed, one port of the            air cylinder rod is powered to remain in its retracted            position        -   b. Once the signal is received from the user (continuous 120            VAC signal which stays on for the entire injection duration)            the relay switch opens and sends power to the other port on            the air cylinder rod to fully extend the rod    -   4. The air cylinder rod moves the plastic slider inside the        steel pipe, which pushes the rubber hose through the boot and        into the truck's chute    -   5. After a pre-determined delay (generally, the time it takes        for the rod to fully extend) the injection system begins        injecting CO₂ into the truck    -   6. The user receives pulses that equate to a mass of injected        CO₂. Once the truck has received its required dosage, the        continuous 120 VAC user signal is removed and the relay switch        goes back to normally closed    -   7. The air cylinder rod retracts, pulling the rubber hose back        into the steel pipe away from any falling materials in the boot    -   8. Once the rod is sufficiently retracted, an “Injection        Complete” message displays on the HMI screen signaling to the        driver that he is clear to pull his truck out from under the        boot

Example 43

This Example provides information on pore water composition in cementslurries treated with various amount of carbon dioxide to carbonate theslurry.

A slurry was made by combining 500 g of cement and 500 g of water in ablender and mixing for 30 s. Combining cement and water was consideredthe start of the experiment. In the case of the control and lowest CO₂dosages samples were removed 2 minutes after the experiment started.Where required CO₂ was introduced to the blender headspace over 2minutes while mixing. This occurred 5 minutes after the experimentstarted. In all cases samples were removed from the blender at 8 and 30minutes after the start of the experiment, representing the period aftercarbonation. Samples were filtered through a 0.22 μm filter cartridge toremove particulate producing a clear filtrate. The filtrate wasacidified using nitric acid and submitted for chemical analysis.

The results are shown in FIGS. 138 and 139. The silicon concentration ofthe pore water at an early time point (8 min) increased with increasingdose of carbon dioxide; even a dose of carbon dioxide as low as 0.05%bwc produced a noticeable increase in pore water silicon concentrationat this time; however, by 30 min, the silicon concentration in the porewater was virtually the same no matter what the dose of carbon dioxideused. Power curves generally shifted to the left with increasing dose ofcarbon dioxide.

Example 44

In this Example, the effects of various degrees of carbonation on earlyand late set time were examined in two different types of cement.

The mix design was: 2700 g sand, 1070 g cement, and 535 g water. Themixing procedure was as follows: Add sand & water—mix 30 s; add half ofcement—mix 30 s; add other half of cement—mix 30 s; mix for additional 2minutes applying CO₂, if required. CO₂ was applied at a flow rate of 20SLPM for periods of 15-120 s to achieve desired level of carbonation.Testing Procedure: Transfer all mix to set time cylinder and allow tosit for ˜2 hrs; perform standard set time test in accordance with ASTMC40.

The results are shown in FIGS. 140 and 141. Both initial (FIG. 140) andfinal (FIG. 141) set were accelerated by carbonation, and, generally,the greater the degree of carbonation, the greater the acceleration ofset. This was true for both Illinois Product cement and St. Mary'sBowmanville cement, though the magnitude of the effect was different foreach.

This Example illustrates that carbonation of a cement mix during mixingcan accelerate set in a manner that is generally dependent on the degreeof carbonation, and also that the magnitude of the effect on set timevaries depending on the type of cement used.

Example 45

In this Example the effects of addition of SCM to carbonated mixes wasinvestigated.

In a first test, the binder in the mix design was cement only: 1350 gsand; 535 g cement; 241 g water; 3 mL ADVA 140 admixture. In a secondtest, the binder in the mix design was cement and fly ash: 8100 g sand;2407 g cement; 802.5 g class C fly ash; 1445 g water; 8.4 mL Zyla 620admixture. In each case, two different cements were used. The mixes werecarbonated at three different doses of carbon dioxide and the 24-hourcompressive strength was compared to non-carbonated mix.

In the mixes with cement only as binder, all doses of carbon dioxideresulted in a lower 24-hour compressible strength compared to controlfor both types of cement (FIG. 142). In contrast, in the mixes withcement and class C fly ash as binder, all doses of carbon dioxideresulted in higher 24-hour compressive strength compared to control forboth types of cement (FIG. 143).

This Example demonstrates that the effect of carbon dioxide is highlymix-dependent, and, in particular, subtle changes in mix chemistry(addition of fly ash) results in noticeable changes to strength responseat 24 hours. A strength improvement was realized when the mix containedfly ash.

Example 46

In this Example, data from 12 different industrial trials were combinedand presented graphically.

Industrial tests of carbonation of concrete mixes were conducted in 12different industrial locations. In most cases, at least two or threedifferent doses of carbon dioxide were used; the results for the bestdose are shown. Thus, the conditions can be considered “semi-optimized,”as a careful determination of the optimum dose was generally not done.The outcomes represent a variety of injection modes (e.g., duringbatching or at a wash rack, single or serial dose); for each differentinjection mode, the results for the best dose are represented. FIG. 144represents strength results, outliers in circles, inner darker bandrepresents middle 50% of results, outer darker band represents 90% ofall results, average result noted. At all time points (1, 3, 7, and 28days) the average compressive strength of the carbonated concrete (bestdose in each trial; best dose size varied with mix design, trialconditions) was 8-12% greater than uncarbonated control. The highestoutlier was about 190% of control compressive strength (1 day) whereasthe lowest outlier was about 98% of control compressive strength (1 dayand 28 days). FIG. 145 represents slump—the average result for CO2conditions were 0.57″ lower than the control, median was 0.50″ lower.This difference was acceptable and within normal variation. FIG. 146represents air—average results for CO2 conditions was 0.40% lower thanthe control, median was 0.20% lower. This difference was acceptable andwithin normal variation.

This Example demonstrates that carbonation of concrete mixes duringmixing consistently produces a mix that has greater compressivestrength, both early and late, compared to non-carbonated mix, withacceptable slump and air characteristics, so long as an optimum dose forthe mix and conditions is chosen.

While preferred embodiments of the present invention have been shown anddescribed herein, it will be obvious to those skilled in the art thatsuch embodiments are provided by way of example only. Numerousvariations, changes, and substitutions will now occur to those skilledin the art without departing from the invention. It should be understoodthat various alternatives to the embodiments of the invention describedherein may be employed in practicing the invention. It is intended thatthe following claims define the scope of the invention and that methodsand structures within the scope of these claims and their equivalents becovered thereby.

What is claimed is:
 1. A cement mix composition, comprising: (i) ahydraulic cement; (ii) water; (iii) carbon dioxide and carbon dioxidereaction products, in amount, measured as carbon dioxide, from 0.01-0.5%by weight cement (bwc), wherein the carbon dioxide reaction productscomprise calcium carbonate; and (iv) particles comprising calciumcarbonate, wherein the particles have an average particle size of lessthan 400 nm, wherein the composition is fluid and capable of being mixedand poured for its intended purpose.
 2. The cement mix composition ofclaim 1, wherein the carbon dioxide and carbon dioxide reaction productsare present in an amount, measured as carbon dioxide, from 0.01-0.3%bwc.
 3. The cement mix composition of claim 1, wherein the carbondioxide and carbon dioxide reaction products are present in an amount,measured as carbon dioxide, from 0.1-0.5%.
 4. The cement mix compositionof claim 1, wherein the particles comprising calcium carbonate arehomogeneously dispersed.
 5. The cement mix composition of claim 1,wherein at least 20% of the calcium carbonate is contained in theparticles with an average particle size of less than 400 nm.
 6. Thecement mix composition of claim 1, wherein the hydraulic cement isPortland cement.
 7. The cement mix composition of claim 6, wherein thePortland cement comprises gypsum.
 8. The cement mix composition of claim1, wherein the calcium carbonate comprises at least 20% amorphouscalcium carbonate.
 9. The cement mix composition of claim 1, wherein thecalcium carbonate comprises at least 20% vaterite.
 10. The cement mixcomposition of claim 1, wherein the calcium carbonate comprises at least20% aragonite.
 11. The cement mix composition of claim 1, wherein thecalcium carbonate comprises at least 20% calcite.
 12. The cement mixcomposition of claim 1, further comprising a supplementary cementitiousmaterial (SCM) comprising fly ash, blast furnace slag, silica fume, or anatural pozzolan.
 13. The cement mix composition of claim 12, where inthe SCM is present in an amount from 1-100% bwc.
 14. The cement mixcomposition of claim 1, wherein the composition is sufficiently fluidand pourable to be poured into a mold at a construction site.
 15. Thecement mix composition of claim 1, wherein the silicon concentration ofpore water in the cement mix is at least 10 parts per million (ppm). 16.A cement mix comprising: (i) reaction products formed in a wet cementmix from reaction of hydraulic cement and water; (ii) reaction productsof carbon dioxide with the hydraulic cement, wherein the reactionproducts comprise calcium carbonate, and wherein the reaction productsof the hydraulic cement and carbon dioxide are present in amount,measured as carbon dioxide, from 0.01-0.5% by weight cement (bwc); and(iii) particles with an average particle size of less than 1 micrometercomprising calcium carbonate, wherein the cement mix is set or hardened.17. The cement mix of claim 16, wherein the reaction products of carbondioxide with the hydraulic cement are present in an amount, measured ascarbon dioxide, from 0.01-0.3% bwc.
 18. The cement mix of claim 16,reaction products of carbon dioxide with the hydraulic cement arepresent in an amount, measured as carbon dioxide, from 0.1-0.5%.
 19. Thecement mix of claim 1, wherein the particles comprising calciumcarbonate are homogeneously dispersed.
 20. The cement mix of claim 16,wherein the reaction products of the hydraulic cement with carbondioxide comprise at least 80% calcium carbonate.
 21. The cement mix ofclaim 20, wherein the at least 50% of the calcium carbonate is containedin the particles with an average particle size less than 1 micrometer.22. The cement mix of claim 16, wherein the hydraulic cement is Portlandcement.
 23. The cement mix of claim 22, wherein the Portland cementcomprises gypsum.
 24. The cement mix of claim 16, wherein the calciumcarbonate comprises at least 20% vaterite.
 25. The cement mix of claim16, wherein the calcium carbonate comprises at least 20% aragonite. 26.The cement mix of claim 16, wherein the calcium carbonate comprises atleast 20% calcite.
 27. The cement mix of claim 16, further comprisingaggregates, so that the hydraulic cement comprises less than 25% byweight of the composition.
 28. The cement mix of claim 16, furthercomprising a supplementary cementitious material (SCM).
 29. The cementmix of claim 28, wherein the SCM comprises fly ash, blast furnace slag,silica fume, or a natural pozzolan.
 30. The cement mix of claim 28,wherein the SCM is present in an amount from 1-100% bwc.